diff --git a/doc/DRAWL.md b/doc/DRAWL.md
index 93db4d8..e072772 100644
--- a/doc/DRAWL.md
+++ b/doc/DRAWL.md
@@ -158,6 +158,8 @@ LISP 1.5 Manual: https://archive.org/details/bitsavers_mitrlelisprammersManual2e
 
 LISP 1.5 Primer: https://www.softwarepreservation.org/projects/LISP/book/Weismann_LISP1.5_Primer_1967.pdf
 
+P-LISP Manual (newer than LISP 1.5): https://archive.org/details/gLISP/gnosisLISPManual
+
 Apple Numerics Manual (SANE): https://vintageapple.org/inside_o/pdf/Apple_Numerics_Manual_Second_Edition_1988.pdf
 
 Video showing DRAWL in action: https://youtu.be/wBMivg6xfSg
diff --git a/src/lisp/s-math.pla b/src/lisp/s-math.pla
index 5568cdc..a90e4e4 100644
--- a/src/lisp/s-math.pla
+++ b/src/lisp/s-math.pla
@@ -710,28 +710,38 @@ def natv_shift(symptr, expr)
     //
     // Shift right
     //
-    while shift < 0
-      bitval[0] = bitval[0] >> 1
-      if bitval[1] & 1
-        bitval[0] = bitval[0] | $8000
-      else
-        bitval[0] = bitval[0] & $7FFF
-      fin
-      bitval[1] = bitval[1] >> 1
-      shift++
-    loop
+    if shift < -31
+      bitval[1] = bitval[1] < 0 ?? $FFFF :: 0
+      bitval[0] = bitval[1]
+    else
+      while shift < 0
+        bitval[0] = bitval[0] >> 1
+        if bitval[1] & 1
+          bitval[0] = bitval[0] | $8000
+        else
+          bitval[0] = bitval[0] & $7FFF
+        fin
+        bitval[1] = bitval[1] >> 1
+        shift++
+      loop
+    fin
   else
     //
     // Shift left
     //
-    while shift > 0
-      bitval[1] = bitval[1] << 1
-      if bitval[0] & $8000
-        bitval[1] = bitval[1] | 1
-      fin
-      bitval[0] = bitval[0] << 1
-      shift--
-    loop
+    if shift > 31
+      bitval[0] = 0
+      bitval[1] = 0
+    else
+      while shift > 0
+        bitval[1] = bitval[1] << 1
+        if bitval[0] & $8000
+          bitval[1] = bitval[1] | 1
+        fin
+        bitval[0] = bitval[0] << 1
+        shift--
+      loop
+    fin
   fin
   return new_int(bitval[0], bitval[1])
 end
@@ -746,6 +756,7 @@ def natv_rotate(symptr, expr)
   symptr    = eval_int(expr=>cdr)
   rotate    = symptr=>intval[0]
   if rotate < 0
+    rotate = rotate | $FFFFFFE0
     while rotate < 0
       wrap      = bitval[0] & 1 ?? $8000 :: 0
       bitval[0] = bitval[0] >> 1
@@ -758,6 +769,7 @@ def natv_rotate(symptr, expr)
       rotate++
     loop
   else
+    rotate = rotate & $0000001F
     while rotate > 0
       wrap      = bitval[1] & $8000 ?? 1 :: 0
       bitval[1] = bitval[1] << 1