diff --git a/src/spicelib/analysis/acan.c b/src/spicelib/analysis/acan.c
index 3a2e79a9e..1bef51747 100644
--- a/src/spicelib/analysis/acan.c
+++ b/src/spicelib/analysis/acan.c
@@ -82,10 +82,18 @@ ACan(CKTcircuit *ckt, int restart)
         switch (job->ACstepType) {
 
         case DECADE:
+            if (job->ACstartFreq <= 0) {
+                fprintf(stderr, "ERROR: AC startfreq <= 0\n");
+                return E_PARMVAL;
+            }
             job->ACfreqDelta =
                 exp(log(10.0)/job->ACnumberSteps);
             break;
         case OCTAVE:
+            if (job->ACstartFreq <= 0) {
+                fprintf(stderr, "ERROR: AC startfreq <= 0\n");
+                return E_PARMVAL;
+            }
             job->ACfreqDelta =
                 exp(log(2.0)/job->ACnumberSteps);
             break;