diff --git a/src/rpmfunctions.c b/src/rpmfunctions.c
index d249874..99675ae 100644
--- a/src/rpmfunctions.c
+++ b/src/rpmfunctions.c
@@ -69,8 +69,10 @@ unsigned int checkVersionWithFlags(const char* cmp1, uint_32 flags, const char*
      struct EVR_s evr1, evr2;
      int vercmp = 0;
 
+     sem_wait(&rpm_mutex);
      rpmEVRparse(cmp1, &evr1);
      rpmEVRparse(cmp2, &evr2);
+     sem_post(&rpm_mutex);
 
      if (strlen(evr1.F[RPMEVR_E]) && strlen(evr2.F[RPMEVR_E])) vercmp=rpmvercmp(evr1.F[RPMEVR_E], evr2.F[RPMEVR_E]);
      else if (strlen(evr2.F[RPMEVR_E])) vercmp = -1;