diff --git a/ChangeLog b/ChangeLog
index a26d58898..b0a01c01d 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -16,6 +16,8 @@ Bugfix
    * Add missing dependencies in test suites that led to build failures
      in configurations that omit certain hashes or public-key algorithms.
      Fixes #1040.
+   * Fix C89 incompatibility in benchmark.c. Contributed by Brendan Shanks.
+     #1353
 
 Changes
    * Support cmake build where Mbed TLS is a subproject. Fix
diff --git a/programs/test/benchmark.c b/programs/test/benchmark.c
index 2864caf84..1945b30d9 100644
--- a/programs/test/benchmark.c
+++ b/programs/test/benchmark.c
@@ -658,13 +658,13 @@ int main( int argc, char *argv[] )
     if( todo.dhm )
     {
         int dhm_sizes[] = { 2048, 3072 };
-        const unsigned char dhm_P_2048[] =
+        static const unsigned char dhm_P_2048[] =
             MBEDTLS_DHM_RFC3526_MODP_2048_P_BIN;
-        const unsigned char dhm_P_3072[] =
+        static const unsigned char dhm_P_3072[] =
             MBEDTLS_DHM_RFC3526_MODP_3072_P_BIN;
-        const unsigned char dhm_G_2048[] =
+        static const unsigned char dhm_G_2048[] =
             MBEDTLS_DHM_RFC3526_MODP_2048_G_BIN;
-        const unsigned char dhm_G_3072[] =
+        static const unsigned char dhm_G_3072[] =
             MBEDTLS_DHM_RFC3526_MODP_3072_G_BIN;
 
         const unsigned char *dhm_P[] = { dhm_P_2048, dhm_P_3072 };