diff --git a/libs/core/basic.cpp b/libs/core/basic.cpp
index 99a25ad2..6c7f1813 100644
--- a/libs/core/basic.cpp
+++ b/libs/core/basic.cpp
@@ -17,9 +17,8 @@ namespace basic {
     //% async
     //% parts="ledmatrix"
     void showNumber(int value, int interval = 150) { 
-      if (interval < 0)
-        return;
-
+      if (interval <= 0)
+        interval = 1;
       ManagedString t(value);
       if (value < 0 || value >= 10) {
         uBit.display.scroll(t, interval);
@@ -55,8 +54,8 @@ namespace basic {
     //% blockId=device_print_message
     //% parts="ledmatrix"
     void showString(StringData *text, int interval = 150) {
-      if (interval < 0)
-        return;
+      if (interval <= 0)
+        interval = 1;
       ManagedString s(text);
       int l = s.length();
       if (l == 0) {
diff --git a/sim/state/ledmatrix.ts b/sim/state/ledmatrix.ts
index 7cb3dae3..1b3d74f3 100644
--- a/sim/state/ledmatrix.ts
+++ b/sim/state/ledmatrix.ts
@@ -234,15 +234,16 @@ namespace pxsim.ImageMethods {
 
 namespace pxsim.basic {
     export function showNumber(x: number, interval: number) {
-        if (interval < 0) return;
-
+        if (interval <= 0)
+            interval = 1;
         let leds = createImageFromString(x.toString());
         if (x < 0 || x >= 10) ImageMethods.scrollImage(leds, 1, interval);
         else showLeds(leds, interval * 5);
     }
 
     export function showString(s: string, interval: number) {
-        if (interval < 0) return;
+        if (interval <= 0)
+            interval = 1;
         if (s.length == 0) {
             clearScreen();
             pause(interval * 5);