diff --git a/std/assembly/array.ts b/std/assembly/array.ts
index 59abb3c9..059d5650 100644
--- a/std/assembly/array.ts
+++ b/std/assembly/array.ts
@@ -344,7 +344,7 @@ export class Array<T> {
     var len = this.length_;
     begin = begin < 0 ? max(begin + len, 0) : min(begin, len);
     end = end < 0 ? max(end + len, 0) : min(end, len);
-    len = end - begin;
+    len = max(end - begin, 0);
     var sliced = new Array<T>(len);
     if (len) {
       memory.copy(
diff --git a/std/assembly/arraybuffer.ts b/std/assembly/arraybuffer.ts
index bef14bdb..9014d73b 100644
--- a/std/assembly/arraybuffer.ts
+++ b/std/assembly/arraybuffer.ts
@@ -52,13 +52,15 @@ export class ArrayBuffer {
 
   slice(begin: i32 = 0, end: i32 = MAX_BLENGTH): ArrayBuffer {
     var len = this.byteLength;
-    if (begin < 0) begin = max(len + begin, 0);
-    else begin = min(begin, len);
-    if (end < 0) end = max(len + end, 0);
-    else end = min(end, len);
-    var newLen = max(end - begin, 0);
-    var buffer = allocateUnsafe(newLen);
-    memory.copy(changetype<usize>(buffer) + HEADER_SIZE, changetype<usize>(this) + HEADER_SIZE + begin, newLen);
+    begin = begin < 0 ? max(len + begin, 0) : min(begin, len);
+    end = end < 0 ? max(len + end, 0) : min(end, len);
+    len = max(end - begin, 0);
+    var buffer = allocateUnsafe(len);
+    memory.copy(
+      changetype<usize>(buffer) + HEADER_SIZE,
+      changetype<usize>(this) + HEADER_SIZE + begin,
+      len
+    );
     return buffer;
   }
 
diff --git a/std/assembly/string.ts b/std/assembly/string.ts
index 70a8527a..b6ca9f73 100644
--- a/std/assembly/string.ts
+++ b/std/assembly/string.ts
@@ -394,10 +394,10 @@ export class String {
   }
 
   slice(beginIndex: i32, endIndex: i32 = i32.MAX_VALUE): String {
-    var length = this.length;
-    var begin = (beginIndex < 0) ? max(beginIndex + length, 0) : min(beginIndex, length);
-    var end = (endIndex < 0) ? max(endIndex + length, 0) : min(endIndex, length);
-    var len = end - begin;
+    var len = this.length;
+    var begin = beginIndex < 0 ? max(beginIndex + len, 0) : min(beginIndex, len);
+    var end = endIndex < 0 ? max(endIndex + len, 0) : min(endIndex, len);
+    len = end - begin;
     if (len <= 0) return changetype<String>("");
     var out = allocateUnsafe(len);
     copyUnsafe(out, 0, this, begin, len);
diff --git a/tests/compiler/std/arraybuffer.optimized.wat b/tests/compiler/std/arraybuffer.optimized.wat
index 67e77e99..1aa4cf2d 100644
--- a/tests/compiler/std/arraybuffer.optimized.wat
+++ b/tests/compiler/std/arraybuffer.optimized.wat
@@ -1437,26 +1437,25 @@
   (local $4 i32)
   local.get $0
   i32.load
-  local.set $4
+  local.set $3
   local.get $1
   i32.const 0
   i32.lt_s
   if (result i32)
    local.get $1
-   local.get $4
-   i32.add
-   local.tee $3
-   i32.const 0
    local.get $3
+   i32.add
+   local.tee $4
+   i32.const 0
+   local.get $4
    i32.const 0
    i32.gt_s
    select
   else   
    local.get $1
-   local.tee $3
-   local.get $4
    local.get $3
-   local.get $4
+   local.get $1
+   local.get $3
    i32.lt_s
    select
   end
@@ -1466,28 +1465,27 @@
   i32.lt_s
   if (result i32)
    local.get $2
-   local.get $4
-   i32.add
-   local.tee $3
-   i32.const 0
    local.get $3
+   i32.add
+   local.tee $4
+   i32.const 0
+   local.get $4
    i32.const 0
    i32.gt_s
    select
   else   
    local.get $2
-   local.tee $3
-   local.get $4
    local.get $3
-   local.get $4
+   local.get $2
+   local.get $3
    i32.lt_s
    select
   end
   local.get $1
   i32.sub
-  local.tee $3
+  local.tee $4
   i32.const 0
-  local.get $3
+  local.get $4
   i32.const 0
   i32.gt_s
   select
diff --git a/tests/compiler/std/arraybuffer.untouched.wat b/tests/compiler/std/arraybuffer.untouched.wat
index 5429c26b..840b04b8 100644
--- a/tests/compiler/std/arraybuffer.untouched.wat
+++ b/tests/compiler/std/arraybuffer.untouched.wat
@@ -1887,14 +1887,13 @@
   (local $5 i32)
   (local $6 i32)
   (local $7 i32)
-  (local $8 i32)
   local.get $0
   i32.load
   local.set $3
   local.get $1
   i32.const 0
   i32.lt_s
-  if
+  if (result i32)
    local.get $3
    local.get $1
    i32.add
@@ -1905,7 +1904,6 @@
    local.get $5
    i32.gt_s
    select
-   local.set $1
   else   
    local.get $1
    local.tee $4
@@ -1915,12 +1913,12 @@
    local.get $5
    i32.lt_s
    select
-   local.set $1
   end
+  local.set $1
   local.get $2
   i32.const 0
   i32.lt_s
-  if
+  if (result i32)
    local.get $3
    local.get $2
    i32.add
@@ -1931,7 +1929,6 @@
    local.get $5
    i32.gt_s
    select
-   local.set $2
   else   
    local.get $2
    local.tee $4
@@ -1941,8 +1938,8 @@
    local.get $5
    i32.lt_s
    select
-   local.set $2
   end
+  local.set $2
   local.get $2
   local.get $1
   i32.sub
@@ -1953,12 +1950,12 @@
   local.get $5
   i32.gt_s
   select
-  local.set $6
-  local.get $6
+  local.set $3
+  local.get $3
   call $~lib/internal/arraybuffer/allocateUnsafe
-  local.set $7
+  local.set $6
   block $~lib/memory/memory.copy|inlined.0
-   local.get $7
+   local.get $6
    i32.const 8
    i32.add
    local.set $4
@@ -1968,14 +1965,14 @@
    local.get $1
    i32.add
    local.set $5
-   local.get $6
-   local.set $8
+   local.get $3
+   local.set $7
    local.get $4
    local.get $5
-   local.get $8
+   local.get $7
    call $~lib/internal/memory/memmove
   end
-  local.get $7
+  local.get $6
  )
  (func $~lib/arraybuffer/ArrayBuffer#slice|trampoline (; 10 ;) (type $iiii) (param $0 i32) (param $1 i32) (param $2 i32) (result i32)
   block $2of2
diff --git a/tests/compiler/std/string.optimized.wat b/tests/compiler/std/string.optimized.wat
index ba824890..3760dc99 100644
--- a/tests/compiler/std/string.optimized.wat
+++ b/tests/compiler/std/string.optimized.wat
@@ -2988,20 +2988,20 @@
   end
   local.get $4
   i32.sub
-  local.tee $2
+  local.tee $3
   i32.const 0
   i32.le_s
   if
    i32.const 256
    return
   end
-  local.get $2
+  local.get $3
   call $~lib/internal/string/allocateUnsafe
   local.tee $1
   i32.const 0
   local.get $0
   local.get $4
-  local.get $2
+  local.get $3
   call $~lib/internal/string/copyUnsafe
   local.get $1
  )
diff --git a/tests/compiler/std/string.untouched.wat b/tests/compiler/std/string.untouched.wat
index b2192b8f..184cd0ca 100644
--- a/tests/compiler/std/string.untouched.wat
+++ b/tests/compiler/std/string.untouched.wat
@@ -3659,7 +3659,6 @@
   (local $6 i32)
   (local $7 i32)
   (local $8 i32)
-  (local $9 i32)
   local.get $0
   i32.load
   local.set $3
@@ -3716,24 +3715,24 @@
   local.get $7
   local.get $6
   i32.sub
-  local.set $8
-  local.get $8
+  local.set $3
+  local.get $3
   i32.const 0
   i32.le_s
   if
    i32.const 256
    return
   end
-  local.get $8
+  local.get $3
   call $~lib/internal/string/allocateUnsafe
-  local.set $9
-  local.get $9
+  local.set $8
+  local.get $8
   i32.const 0
   local.get $0
   local.get $6
-  local.get $8
+  local.get $3
   call $~lib/internal/string/copyUnsafe
-  local.get $9
+  local.get $8
  )
  (func $~lib/string/String#slice|trampoline (; 35 ;) (type $iiii) (param $0 i32) (param $1 i32) (param $2 i32) (result i32)
   block $1of1