diff --git a/.gitignore b/.gitignore
index 4a214dc1..89921218 100644
--- a/.gitignore
+++ b/.gitignore
@@ -1,4 +1,4 @@
 images/*
 v86_all.js
-cpu.js
+src/cpu.js
 
diff --git a/src/cpu.js b/src/cpu.js
index 6c53bc7c..a080e0d6 100644
--- a/src/cpu.js
+++ b/src/cpu.js
@@ -5550,7 +5550,7 @@ function FPU(io)
             case 2:
                 // fist
                 var st0 = get_st0();
-                if(st0 <= 0x7FFF || st0 >= -0x8000)
+                if(st0 <= 0x7FFF && st0 >= -0x8000)
                 {
                     safe_write16(addr, integer_round(st0));
                 }
@@ -5563,7 +5563,7 @@ function FPU(io)
             case 3:
                 // fistp
                 var st0 = get_st0();
-                if(st0 <= 0x7FFF || st0 >= -0x8000)
+                if(st0 <= 0x7FFF && st0 >= -0x8000)
                 {
                     safe_write16(addr, integer_round(st0));
                 }
diff --git a/src/fpu.macro.js b/src/fpu.macro.js
index 0f8dc40d..51f76656 100644
--- a/src/fpu.macro.js
+++ b/src/fpu.macro.js
@@ -1633,7 +1633,7 @@ function FPU(io)
                 // fistp
                 var st0 = integer_round(get_st0());
 
-                if(!(st0 <= 0x7FFFFFFFFFFFFFFF || st0 >= -0x8000000000000000))
+                if(!(st0 <= 0x7FFFFFFFFFFFFFFF && st0 >= -0x8000000000000000))
                 {
                     st0 = 0x8000000000000000;
                     invalid_arithmatic();