diff --git a/src/cli/commands/repo/gc.js b/src/cli/commands/repo/gc.js
index b805ac9934..5eb6d7a672 100644
--- a/src/cli/commands/repo/gc.js
+++ b/src/cli/commands/repo/gc.js
@@ -27,7 +27,7 @@ module.exports = {
         if (r.err) {
           streamErrors && print(r.err.message, true, true)
         } else {
-          print((quiet ? '' : 'removed ') + r.cid)
+          print((quiet ? '' : 'removed ') + r.multihash)
         }
       }
     })())
diff --git a/src/core/components/pin/gc.js b/src/core/components/pin/gc.js
index a974a85de5..8c272ef83b 100644
--- a/src/core/components/pin/gc.js
+++ b/src/core/components/pin/gc.js
@@ -3,7 +3,6 @@
 const CID = require('cids')
 const base32 = require('base32.js')
 const callbackify = require('callbackify')
-const { cidToString } = require('../../../utils/cid')
 const log = require('debug')('ipfs:gc')
 const { default: Queue } = require('p-queue')
 // TODO: Use exported key from root when upgraded to ipfs-mfs@>=13
@@ -47,7 +46,7 @@ module.exports = function gc (self) {
   })
 }
 
-// Get Set of CIDs of blocks to keep
+// Get Set of multihashes of blocks to keep
 async function createMarkedSet (ipfs) {
   const output = new Set()
 
@@ -55,7 +54,8 @@ async function createMarkedSet (ipfs) {
     log(`Found ${pins.length} pinned blocks`)
 
     pins.forEach(pin => {
-      output.add(cidToString(new CID(pin), { base: 'base32' }))
+      const cid = new CID(pin)
+      output.add(base32.encode(cid.multihash))
     })
   }
 
@@ -91,7 +91,6 @@ async function getDescendants (ipfs, cid) {
   const refs = await ipfs.refs(cid, { recursive: true })
   const cids = [cid, ...refs.map(r => new CID(r.ref))]
   log(`Found ${cids.length} MFS blocks`)
-  // log('  ' + cids.join('\n  '))
 
   return cids
 }
@@ -100,54 +99,37 @@ async function getDescendants (ipfs, cid) {
 async function deleteUnmarkedBlocks (ipfs, markedSet, blockKeys) {
   // Iterate through all blocks and find those that are not in the marked set
   // The blockKeys variable has the form [ { key: Key() }, { key: Key() }, ... ]
-  const unreferenced = []
   const result = []
+  let blockCounter = 0
 
   const queue = new Queue({
     concurrency: BLOCK_RM_CONCURRENCY
   })
 
   for await (const { key: k } of blockKeys) {
-    try {
-      const cid = dsKeyToCid(k)
-      const b32 = cid.toV1().toString('base32')
-      if (!markedSet.has(b32)) {
-        unreferenced.push(cid)
-
-        queue.add(async () => {
-          const res = {
-            cid
-          }
-
-          try {
-            await ipfs._repo.blocks.delete(cid)
-          } catch (err) {
-            res.err = new Error(`Could not delete block with CID ${cid}: ${err.message}`)
-          }
-
-          result.push(res)
-        })
-      }
-    } catch (err) {
-      const msg = `Could not convert block with key '${k}' to CID`
-      log(msg, err)
-      result.push({ err: new Error(msg + `: ${err.message}`) })
+    blockCounter++
+    const multihashString = k.toString().substr(1)
+    if (!markedSet.has(multihashString)) {
+      queue.add(async () => {
+        const res = {
+          multihash: multihashString
+        }
+
+        try {
+          await ipfs._repo.blocks.delete(base32.decode(multihashString))
+        } catch (err) {
+          res.err = new Error(`Could not delete block with multihash ${multihashString}: ${err.message}`)
+        }
+
+        result.push(res)
+      })
     }
   }
 
   await queue.onIdle()
 
-  log(`Marked set has ${markedSet.size} unique blocks. Blockstore has ${blockKeys.length} blocks. ` +
-  `Deleted ${unreferenced.length} blocks.`)
+  log(`Marked set has ${markedSet.size} unique blocks. Blockstore has ${blockCounter} blocks. ` +
+    `Deleted ${result.filter(res => res.err === undefined).length} blocks.`)
 
   return result
 }
-
-// TODO: Use exported utility when upgrade to ipfs-repo@>=0.27.1
-// https://github.com/ipfs/js-ipfs-repo/pull/206
-function dsKeyToCid (key) {
-  // Block key is of the form /<base32 encoded string>
-  const decoder = new base32.Decoder()
-  const buff = decoder.write(key.toString().slice(1)).finalize()
-  return new CID(Buffer.from(buff))
-}
diff --git a/src/http/api/resources/repo.js b/src/http/api/resources/repo.js
index 108ce6abda..39768223e8 100644
--- a/src/http/api/resources/repo.js
+++ b/src/http/api/resources/repo.js
@@ -18,7 +18,7 @@ exports.gc = {
     const response = filtered.map(r => {
       return {
         Err: r.err && r.err.message,
-        Key: !r.err && { '/': r.cid.toString() }
+        Key: !r.err && r.multihash
       }
     })
     return h.response(response)
diff --git a/test/core/gc.spec.js b/test/core/gc.spec.js
index 42022f3fed..059ffb3bbc 100644
--- a/test/core/gc.spec.js
+++ b/test/core/gc.spec.js
@@ -7,6 +7,8 @@ const IPFSFactory = require('ipfsd-ctl')
 const pEvent = require('p-event')
 const env = require('ipfs-utils/src/env')
 const IPFS = require('../../src/core')
+const CID = require('cids')
+const base32 = require('base32.js')
 const { Errors } = require('interface-datastore')
 
 // We need to detect when a readLock or writeLock is requested for the tests
@@ -90,17 +92,17 @@ describe('gc', function () {
     name: 'add',
     add1: () => ipfs.add(fixtures[0], { pin: false }),
     add2: () => ipfs.add(fixtures[1], { pin: false }),
-    resToCid: (res) => res[0].hash
+    resToMultihash: (res) => base32.encode(new CID(res[0].hash).multihash)
   }, {
     name: 'object put',
     add1: () => ipfs.object.put({ Data: 'obj put 1', Links: [] }),
     add2: () => ipfs.object.put({ Data: 'obj put 2', Links: [] }),
-    resToCid: (res) => res.toString()
+    resToMultihash: (res) => base32.encode(res.multihash)
   }, {
     name: 'block put',
     add1: () => ipfs.block.put(Buffer.from('block put 1'), null),
     add2: () => ipfs.block.put(Buffer.from('block put 2'), null),
-    resToCid: (res) => res.cid.toString()
+    resToMultihash: (res) => base32.encode(res.cid.multihash)
   }]
 
   describe('locks', function () {
@@ -122,9 +124,9 @@ describe('gc', function () {
         await gcStarted
         const add2 = test.add2()
 
-        const deleted = (await gc).map(i => i.cid.toString())
-        const add1Res = test.resToCid(await add1)
-        const add2Res = test.resToCid(await add2)
+        const deleted = (await gc).map(i => i.multihash)
+        const add1Res = test.resToMultihash(await add1)
+        const add2Res = test.resToMultihash(await add2)
 
         // Should have garbage collected blocks from first add, because GC should
         // have waited for first add to finish
@@ -152,9 +154,9 @@ describe('gc', function () {
       await gcStarted
       const add2 = ipfs.add(fixtures[3], { pin: true })
 
-      const deleted = (await gc).map(i => i.cid.toString())
-      const add1Res = (await add1)[0].hash
-      const add2Res = (await add2)[0].hash
+      const deleted = (await gc).map(i => i.multihash)
+      const add1Res = base32.encode(new CID((await add1)[0].hash).multihash)
+      const add2Res = base32.encode(new CID((await add2)[0].hash).multihash)
 
       // Should not have garbage collected blocks from first add, because GC should
       // have waited for first add + pin to finish (protected by pin)
@@ -168,7 +170,9 @@ describe('gc', function () {
     it('garbage collection should wait for pending block rm to finish', async () => {
       // Add two blocks so that we can remove them
       const cid1 = (await ipfs.block.put(Buffer.from('block to rm 1'), null)).cid
+      const cid1Multihash = base32.encode(cid1.multihash)
       const cid2 = (await ipfs.block.put(Buffer.from('block to rm 2'), null)).cid
+      const cid2Multihash = base32.encode(cid2.multihash)
 
       // Remove first block from IPFS
       // Note: block rm will take a write lock
@@ -185,33 +189,34 @@ describe('gc', function () {
       await gcStarted
       const rm2 = ipfs.block.rm(cid2)
 
-      const deleted = (await gc).map(i => i.cid.toString())
-      await rm1
-
-      // Second rm should fail because GC has already removed that block
-      try {
-        await rm2
-      } catch (err) {
-        expect(err.code).eql(Errors.dbDeleteFailedError().code)
-      }
+      const deleted = (await gc).map(i => i.multihash)
+      const rm1Out = await rm1
+      expect(rm1Out[0]).to.not.have.property('error')
 
       // Confirm second block has been removed
-      const localRefs = (await ipfs.refs.local()).map(r => r.ref)
-      expect(localRefs).not.includes(cid2.toString())
+      const localMultihashes = (await ipfs.refs.local()).map(r => base32.encode(new CID(r.ref).multihash))
+      expect(localMultihashes).not.includes(cid2Multihash)
+
+      // Second rm should fail because GC has already removed that block
+      expect((await rm2)[0])
+        .to.have.property('error')
+        .that.has.property('code').that.equal(Errors.dbDeleteFailedError().code)
 
       // Should not have garbage collected block from first block put, because
       // GC should have waited for first rm (removing first block put) to finish
-      expect(deleted).not.includes(cid1.toString())
+      expect(deleted).not.includes(cid1Multihash)
 
       // Should have garbage collected block from second block put, because GC
       // should have completed before second rm (removing second block put)
-      expect(deleted).includes(cid2.toString())
+      expect(deleted).includes(cid2Multihash)
     })
 
     it('garbage collection should wait for pending pin add to finish', async () => {
       // Add two blocks so that we can pin them
-      const cid1 = (await ipfs.block.put(Buffer.from('block to pin add 1'), null)).cid
-      const cid2 = (await ipfs.block.put(Buffer.from('block to pin add 2'), null)).cid
+      const cid1 = (await ipfs.block.put(Buffer.from('block to test pin add 1'), null)).cid
+      const cid2 = (await ipfs.block.put(Buffer.from('block to test pin add 2'), null)).cid
+      const cid1Multihash = base32.encode(cid1.multihash)
+      const cid2Multihash = base32.encode(cid2.multihash)
 
       // Pin first block
       // Note: pin add will take a read lock
@@ -221,7 +226,7 @@ describe('gc', function () {
       // Once pin lock has been requested, start GC
       await pinLockRequested
       const gc = ipfs.repo.gc()
-      const deleted = (await gc).map(i => i.cid.toString())
+      const deleted = (await gc).map(i => i.multihash)
       await pin1
 
       // TODO: Adding pin for removed block never returns, which means the lock
@@ -229,22 +234,24 @@ describe('gc', function () {
       // const pin2 = ipfs.pin.add(cid2)
 
       // Confirm second second block has been removed
-      const localRefs = (await ipfs.refs.local()).map(r => r.ref)
-      expect(localRefs).not.includes(cid2.toString())
+      const localMultihashes = (await ipfs.refs.local()).map(r => base32.encode(new CID(r.ref).multihash))
+      expect(localMultihashes).not.includes(cid2Multihash)
 
       // Should not have garbage collected block from first block put, because
       // GC should have waited for pin (protecting first block put) to finish
-      expect(deleted).not.includes(cid1.toString())
+      expect(deleted).not.includes(cid1Multihash)
 
       // Should have garbage collected block from second block put, because GC
       // should have completed before second pin
-      expect(deleted).includes(cid2.toString())
+      expect(deleted).includes(cid2Multihash)
     })
 
     it('garbage collection should wait for pending pin rm to finish', async () => {
       // Add two blocks so that we can pin them
       const cid1 = (await ipfs.block.put(Buffer.from('block to pin rm 1'), null)).cid
       const cid2 = (await ipfs.block.put(Buffer.from('block to pin rm 2'), null)).cid
+      const cid1Multihash = base32.encode(cid1.multihash)
+      const cid2Multihash = base32.encode(cid2.multihash)
 
       // Pin blocks
       await ipfs.pin.add(cid1)
@@ -265,17 +272,17 @@ describe('gc', function () {
       await gcStarted
       const pinRm2 = ipfs.pin.rm(cid2)
 
-      const deleted = (await gc).map(i => i.cid.toString())
+      const deleted = (await gc).map(i => i.multihash)
       await pinRm1
       await pinRm2
 
       // Should have garbage collected block from first block put, because
       // GC should have waited for pin rm (unpinning first block put) to finish
-      expect(deleted).includes(cid1.toString())
+      expect(deleted).includes(cid1Multihash)
 
       // Should not have garbage collected block from second block put, because
       // GC should have completed before second block was unpinned
-      expect(deleted).not.includes(cid2.toString())
+      expect(deleted).not.includes(cid2Multihash)
     })
   })
 })