diff --git a/common/lfdemod.c b/common/lfdemod.c
index 7b899e99e..b6869ba43 100644
--- a/common/lfdemod.c
+++ b/common/lfdemod.c
@@ -1663,6 +1663,7 @@ int askdemod_ext(uint8_t *bits, size_t *size, int *clk, int *invert, int maxErr,
         return errCnt;
     }
 
+    *startIdx = start - (*clk / 2);
     if (g_debugMode == 2) prnt("DEBUG: (askdemod_ext) Weak wave detected: startIdx %i", *startIdx);
 
     int lastBit;  //set first clock check - can go negative