diff --git a/src/interfaces/ecpg/pgtypeslib/dt_common.c b/src/interfaces/ecpg/pgtypeslib/dt_common.c
index 0d63fe52c5b..bf5976cf03b 100644
--- a/src/interfaces/ecpg/pgtypeslib/dt_common.c
+++ b/src/interfaces/ecpg/pgtypeslib/dt_common.c
@@ -2327,10 +2327,10 @@ DecodeDateTime(char **field, int *ftype, int nf,
 			return ((fmask & DTK_TIME_M) == DTK_TIME_M) ? 1 : -1;
 
 		/*
-		 * check for valid day of month, now that we know for sure the month
+		 * check for valid day of month and month, now that we know for sure the month
 		 * and year...
 		 */
-		if (tm->tm_mday < 1 || tm->tm_mday > day_tab[isleap(tm->tm_year)][tm->tm_mon - 1])
+		if (tm->tm_mon < 1 || tm->tm_mday < 1 || tm->tm_mday > day_tab[isleap(tm->tm_year)][tm->tm_mon - 1])
 			return -1;
 
 		/*