diff --git a/src/toolsrc/sb.pla b/src/toolsrc/sb.pla
index 6c78c6d..66ae781 100644
--- a/src/toolsrc/sb.pla
+++ b/src/toolsrc/sb.pla
@@ -811,21 +811,17 @@ end
 asm isalpha
         LDY     #$00
         LDA     ESTKL,X
+        CMP     #'_'
+        BEQ     ISALTRU
         CMP     #'A'
         BCC     ISALRET
         CMP     #'Z'+1
-        BCS     +
-        DEY
-        BNE     ISALRET
-+       CMP     #'a'
+	BCC	ISALTRU
+        CMP     #'a'
         BCC     ISALRET
         CMP     #'z'+1
-        BCS     +
-        DEY
-        BNE     ISALRET
-+       CMP     #'_'
-        BNE     ISALRET
-        DEY
+        BCS	ISALRET
+ISALTRU DEY
 ISALRET STY     ESTKL,X
         STY     ESTKH,X
         RTS
@@ -863,27 +859,21 @@ end
 asm isalphanum
         LDY     #$00
         LDA     ESTKL,X
+        CMP     #'_'
+        BEQ     ISANTRU
         CMP     #'0'
         BCC     ISANRET
         CMP     #'9'+1
-        BCS     +
-        DEY
-        BNE     ISANRET
-+       CMP     #'A'
+        BCC	ISANTRU
+        CMP     #'A'
         BCC     ISANRET
         CMP     #'Z'+1
-        BCS     +
-        DEY
-        BNE     ISANRET
-+       CMP     #'a'
+        BCC	ISANTRU
+        CMP     #'a'
         BCC     ISANRET
         CMP     #'z'+1
-        BCS     +
-        DEY
-        BNE     ISANRET
-+       CMP     #'_'
-        BNE     ISANRET
-        DEY
+        BCS	ISANRET
+ISANTRU DEY
 ISANRET STY     ESTKL,X
         STY     ESTKH,X
         RTS