diff --git a/src/viminfo.c b/src/viminfo.c
index 58bf419..540422c 100644
--- a/src/viminfo.c
+++ b/src/viminfo.c
@@ -1068,7 +1068,7 @@
 	    }
 	}
 
-	if (isdigit(*p))
+	if (SAFE_isdigit(*p))
 	{
 	    value->bv_type = BVAL_NR;
 	    value->bv_nr = getdigits(&p);
@@ -2485,7 +2485,7 @@
     str = virp->vir_line + 1;
     if (*str <= 127
 	    && ((*virp->vir_line == '\''
-				       && (VIM_ISDIGIT(*str) || isupper(*str)))
+				       && (VIM_ISDIGIT(*str) || SAFE_isupper(*str)))
 	     || (*virp->vir_line == '-' && *str == '\'')))
     {
 	if (*str == '\'')