diff --git a/crates/roc_std/src/lib.rs b/crates/roc_std/src/lib.rs
index f8877cae10..219652cbd9 100644
--- a/crates/roc_std/src/lib.rs
+++ b/crates/roc_std/src/lib.rs
@@ -384,14 +384,19 @@ impl RocDec {
         // push a dummy character so we have space for the decimal dot
         string.push('$');
 
-        // Safety: at any time, the string only contains ascii characters, so it is always valid utf8
-        let bytes = unsafe { string.as_bytes_mut() };
+        if decimal_location == last_nonzero_byte {
+            // never have a '.' as the last character
+            string.truncate(last_nonzero_byte)
+        } else {
+            // Safety: at any time, the string only contains ascii characters, so it is always valid utf8
+            let bytes = unsafe { string.as_bytes_mut() };
 
-        // shift the fractional part by one
-        bytes.copy_within(decimal_location..last_nonzero_byte, decimal_location + 1);
+            // shift the fractional part by one
+            bytes.copy_within(decimal_location..last_nonzero_byte, decimal_location + 1);
 
-        // and put in the decimal dot in the right place
-        bytes[decimal_location] = b'.';
+            // and put in the decimal dot in the right place
+            bytes[decimal_location] = b'.';
+        }
 
         string.as_str()
     }