diff --git a/client/src/graph.c b/client/src/graph.c
index 2d75f3d30..6ce443155 100644
--- a/client/src/graph.c
+++ b/client/src/graph.c
@@ -247,7 +247,10 @@ int GetPskClock(const char *str, bool printAns) {
     size_t firstPhaseShiftLoc = 0;
     uint8_t curPhase = 0, fc = 0;
     clock1 = DetectPSKClock(bits, size, 0, &firstPhaseShiftLoc, &curPhase, &fc);
-    setClockGrid(clock1, firstPhaseShiftLoc);
+
+    if (clock1 >= 0)
+        setClockGrid(clock1, firstPhaseShiftLoc);
+
     // Only print this message if we're not looping something
     if (printAns)
         PrintAndLogEx(SUCCESS, "Auto-detected clock rate: %d", clock1);