diff --git a/Sources/GoogleAI/GenerativeModel.swift b/Sources/GoogleAI/GenerativeModel.swift
index d59f660..f5e4b21 100644
--- a/Sources/GoogleAI/GenerativeModel.swift
+++ b/Sources/GoogleAI/GenerativeModel.swift
@@ -108,10 +108,7 @@ public final class GenerativeModel {
     do {
       response = try await generativeAIService.loadRequest(request: generateContentRequest)
     } catch {
-      if let error = error as? RPCError, error.isInvalidAPIKeyError() {
-        throw GenerateContentError.invalidAPIKey
-      }
-      throw GenerateContentError.internalError(underlying: error)
+      throw GenerativeModel.generateContentError(from: error)
     }
 
     // Check the prompt feedback to see if the prompt was blocked.
@@ -168,7 +165,7 @@ public final class GenerativeModel {
       do {
         response = try await responseIterator.next()
       } catch {
-        throw GenerateContentError.internalError(underlying: error)
+        throw GenerativeModel.generateContentError(from: error)
       }
 
       // The responseIterator will return `nil` when it's done.
@@ -240,6 +237,18 @@ public final class GenerativeModel {
       return modelResourcePrefix + name
     }
   }
+
+  /// Returns a `GenerateContentError` (for public consumption) from an internal error.
+  ///
+  /// If `error` is already a `GenerateContentError` the error is returned unchanged.
+  private static func generateContentError(from error: Error) -> GenerateContentError {
+    if let error = error as? GenerateContentError {
+      return error
+    } else if let error = error as? RPCError, error.isInvalidAPIKeyError() {
+      return GenerateContentError.invalidAPIKey
+    }
+    return GenerateContentError.internalError(underlying: error)
+  }
 }
 
 /// See ``GenerativeModel/countTokens(_:)-9spwl``.
diff --git a/Tests/GoogleAITests/GenerativeModelTests.swift b/Tests/GoogleAITests/GenerativeModelTests.swift
index bb50e65..db19ddc 100644
--- a/Tests/GoogleAITests/GenerativeModelTests.swift
+++ b/Tests/GoogleAITests/GenerativeModelTests.swift
@@ -439,6 +439,26 @@ final class GenerativeModelTests: XCTestCase {
 
   // MARK: - Generate Content (Streaming)
 
+  func testGenerateContentStream_failureInvalidAPIKey() async throws {
+    MockURLProtocol
+      .requestHandler = try httpRequestHandler(
+        forResource: "unary-failure-api-key",
+        withExtension: "json"
+      )
+
+    do {
+      let stream = model.generateContentStream("Hi")
+      for try await _ in stream {
+        XCTFail("No content is there, this shouldn't happen.")
+      }
+    } catch GenerateContentError.invalidAPIKey {
+      // invalidAPIKey error is as expected, nothing else to check.
+      return
+    }
+
+    XCTFail("Should have caught an error.")
+  }
+
   func testGenerateContentStream_failureEmptyContent() async throws {
     MockURLProtocol
       .requestHandler = try httpRequestHandler(