diff --git a/easybuild/easyblocks/h/hdf5.py b/easybuild/easyblocks/h/hdf5.py
index 06b82c635b..f96942e841 100644
--- a/easybuild/easyblocks/h/hdf5.py
+++ b/easybuild/easyblocks/h/hdf5.py
@@ -77,10 +77,16 @@ def configure_step(self):
         self.cfg.update('configopts', "--with-pic --with-pthread --enable-shared")
         self.cfg.update('configopts', "--enable-cxx --enable-fortran %s" % fcomp)
 
+        # make C API thread safe (C++ / FORTRAN APIs are unaffected)
+        self.cfg.update('configopts', "--enable-threadsafe")
+
+        # --enable-unsupported is needed to allow --enable-threadsafe to be used together with --enable-cxx
+        self.cfg.update('configopts', "--enable-unsupported")
+
         # MPI and C++ support enabled requires --enable-unsupported, because this is untested by HDF5
         # also returns False if MPI is not supported by this toolchain
         if self.toolchain.options.get('usempi', None):
-            self.cfg.update('configopts', "--enable-unsupported --enable-parallel")
+            self.cfg.update('configopts', "--enable-parallel")
             mpich_mpi_families = [toolchain.INTELMPI, toolchain.MPICH, toolchain.MPICH2, toolchain.MVAPICH2]
             if self.toolchain.mpi_family() in mpich_mpi_families:
                 self.cfg.update('buildopts', 'CXXFLAGS="$CXXFLAGS -DMPICH_IGNORE_CXX_SEEK"')