diff --git a/openblas.spec b/openblas.spec
index 4016e83..3e2aef8 100644
--- a/openblas.spec
+++ b/openblas.spec
@@ -15,7 +15,7 @@
 
 Name:           openblas
 Version:        0.3.9
-Release:        2%{?dist}
+Release:        3%{?dist}
 Summary:        An optimized BLAS library based on GotoBLAS2
 License:        BSD
 URL:            https://github.com/xianyi/OpenBLAS/
@@ -398,12 +398,12 @@ FCOMMON="%{optflags} -fPIC -frecursive"
 # Use Fedora linker flags
 export LDFLAGS="%{__global_ldflags}"
 
-make -C Rblas      $TARGET USE_THREAD=0 USE_OPENMP=0 FC=gfortran CC=gcc COMMON_OPT="$COMMON" FCOMMON_OPT="$FCOMMON" $NMAX LIBPREFIX="libRblas" LIBSONAME="libRblas.so" $AVX $LAPACKE INTERFACE64=0
+make -C Rblas      $TARGET USE_THREAD=0 USE_LOCKING=1 USE_OPENMP=0 FC=gfortran CC=gcc COMMON_OPT="$COMMON" FCOMMON_OPT="$FCOMMON" $NMAX LIBPREFIX="libRblas" LIBSONAME="libRblas.so" $AVX $LAPACKE INTERFACE64=0
 
 # Declare some necessary build flags
 COMMON="%{optflags} -fPIC"
 FCOMMON="$COMMON -frecursive"
-make -C serial     $TARGET USE_THREAD=0 USE_OPENMP=0 FC=gfortran CC=gcc COMMON_OPT="$COMMON" FCOMMON_OPT="$FCOMMON" $NMAX LIBPREFIX="libopenblas"      $AVX $LAPACKE INTERFACE64=0
+make -C serial     $TARGET USE_THREAD=0 USE_LOCKING=1 USE_OPENMP=0 FC=gfortran CC=gcc COMMON_OPT="$COMMON" FCOMMON_OPT="$FCOMMON" $NMAX LIBPREFIX="libopenblas"      $AVX $LAPACKE INTERFACE64=0
 make -C threaded   $TARGET USE_THREAD=1 USE_OPENMP=0 FC=gfortran CC=gcc COMMON_OPT="$COMMON" FCOMMON_OPT="$FCOMMON" $NMAX LIBPREFIX="libopenblasp"     $AVX $LAPACKE INTERFACE64=0
 
 # USE_THREAD determines use of SMP, not of pthreads
@@ -414,7 +414,7 @@ make -C openmp     $TARGET USE_THREAD=1 USE_OPENMP=1 FC=gfortran CC=gcc COMMON_O
 %if %build64
 COMMON="%{optflags} -fPIC"
 FCOMMON="$COMMON -frecursive -fdefault-integer-8"
-make -C serial64   $TARGET USE_THREAD=0 USE_OPENMP=0 FC=gfortran CC=gcc COMMON_OPT="$COMMON" FCOMMON_OPT="$FCOMMON" $NMAX LIBPREFIX="libopenblas64"    $AVX $LAPACKE INTERFACE64=1
+make -C serial64   $TARGET USE_THREAD=0 USE_LOCKING=1 USE_OPENMP=0 FC=gfortran CC=gcc COMMON_OPT="$COMMON" FCOMMON_OPT="$FCOMMON" $NMAX LIBPREFIX="libopenblas64"    $AVX $LAPACKE INTERFACE64=1
 make -C threaded64 $TARGET USE_THREAD=1 USE_OPENMP=0 FC=gfortran CC=gcc COMMON_OPT="$COMMON" FCOMMON_OPT="$FCOMMON" $NMAX LIBPREFIX="libopenblasp64"   $AVX $LAPACKE INTERFACE64=1
 
 COMMON="%{optflags} -fPIC -fopenmp -pthread"
@@ -423,7 +423,7 @@ make -C openmp64   $TARGET USE_THREAD=1 USE_OPENMP=1 FC=gfortran CC=gcc COMMON_O
 
 COMMON="%{optflags} -fPIC"
 FCOMMON="$COMMON -frecursive  -fdefault-integer-8"
-make -C serial64_   $TARGET USE_THREAD=0 USE_OPENMP=0 FC=gfortran CC=gcc COMMON_OPT="$COMMON" FCOMMON_OPT="$FCOMMON" $NMAX LIBPREFIX="libopenblas64_"  $AVX $LAPACKE INTERFACE64=1 SYMBOLSUFFIX=64_
+make -C serial64_   $TARGET USE_THREAD=0 USE_LOCKING=1 USE_OPENMP=0 FC=gfortran CC=gcc COMMON_OPT="$COMMON" FCOMMON_OPT="$FCOMMON" $NMAX LIBPREFIX="libopenblas64_"  $AVX $LAPACKE INTERFACE64=1 SYMBOLSUFFIX=64_
 make -C threaded64_ $TARGET USE_THREAD=1 USE_OPENMP=0 FC=gfortran CC=gcc COMMON_OPT="$COMMON" FCOMMON_OPT="$FCOMMON" $NMAX LIBPREFIX="libopenblasp64_" $AVX $LAPACKE INTERFACE64=1 SYMBOLSUFFIX=64_
 
 COMMON="%{optflags} -fPIC -fopenmp -pthread"
@@ -668,6 +668,10 @@ rm -rf %{buildroot}%{_libdir}/pkgconfig
 %endif
 
 %changelog
+* Thu May 28 2020 Susi Lehtola <jussilehtola@fedoraproject.org> - 0.3.9-3
+- Enable USE_LOCKING in the sequential versions of the library for
+  thread safety.
+
 * Thu Apr 02 2020 Susi Lehtola <jussilehtola@fedoraproject.org> - 0.3.9-2
 - Patch for BZ #1820131.