diff --git a/jpm b/jpm
index 4e52df62..320393e7 100755
--- a/jpm
+++ b/jpm
@@ -23,12 +23,12 @@
 
 # Overriden on some installs.
 # To configure this script, replace the code between
-# the START and END comments and define a function 
+# the START and END comments and define a function
 # (install-paths) that gives the the default paths
 # to use. Trailing directory separator not expected.
 #
 # Example.
-# 
+#
 #   (defn- install-paths []
 #     {:headerpath "/usr/local/include/janet"
 #      :libpath "/usr/local/lib/janet"
@@ -169,9 +169,7 @@
   [& args]
   (if (dyn :verbose)
     (print ;(interpose " " args)))
-  (def res (os/execute args :p))
-  (unless (zero? res)
-    (error (string "command exited with status " res))))
+  (os/execute args :px))
 
 (defn copy
   "Copy a file or directory recursively from one location to another."
@@ -1424,26 +1422,30 @@ Flags are:
    "load-lockfile" load-lockfile
    "quickbin" quickbin})
 
-(def- args (tuple/slice (dyn :args) 1))
-(def- len (length args))
-(var i :private 0)
+(defn- main
+  "Script entry."
+  [& argv]
 
-# Get flags
-(while (< i len)
-  (if-let [m (peg/match argpeg (args i))]
-    (if (= 2 (length m))
-      (let [[key value] m]
-        (setdyn (keyword key) value))
-      (setdyn (keyword (m 0)) true))
-    (break))
-  (++ i))
+  (def- args (tuple/slice argv 1))
+  (def- len (length args))
+  (var i :private 0)
 
-# Run subcommand
-(if (= i len)
-  (help)
-  (do
-    (if-let [com (subcommands (args i))]
-      (com ;(tuple/slice args (+ i 1)))
-      (do
-        (print "invalid command " (args i))
-        (help)))))
+  # Get flags
+  (while (< i len)
+    (if-let [m (peg/match argpeg (args i))]
+      (if (= 2 (length m))
+        (let [[key value] m]
+          (setdyn (keyword key) value))
+        (setdyn (keyword (m 0)) true))
+      (break))
+    (++ i))
+
+  # Run subcommand
+  (if (= i len)
+    (help)
+    (do
+      (if-let [com (subcommands (args i))]
+        (com ;(tuple/slice args (+ i 1)))
+        (do
+          (print "invalid command " (args i))
+          (help))))))
diff --git a/src/core/vm.c b/src/core/vm.c
index 0c832122..31f7465e 100644
--- a/src/core/vm.c
+++ b/src/core/vm.c
@@ -1378,6 +1378,7 @@ static JanetSignal janet_continue_no_check(JanetFiber *fiber, Janet in, Janet *o
         if (janet_vm_root_fiber == fiber) janet_vm_root_fiber = NULL;
         if (sig != JANET_SIGNAL_OK && !(child->flags & (1 << sig))) {
             *out = in;
+            janet_fiber_set_status(fiber, sig);
             return sig;
         }
         /* Check if we need any special handling for certain opcodes */
@@ -1417,23 +1418,23 @@ static JanetSignal janet_continue_no_check(JanetFiber *fiber, Janet in, Janet *o
 
     /* Save global state */
     JanetTryState tstate;
-    JanetSignal signal = janet_try(&tstate);
-    if (!signal) {
+    JanetSignal sig = janet_try(&tstate);
+    if (!sig) {
         /* Normal setup */
         if (janet_vm_root_fiber == NULL) janet_vm_root_fiber = fiber;
         janet_vm_fiber = fiber;
         janet_fiber_set_status(fiber, JANET_STATUS_ALIVE);
-        signal = run_vm(fiber, in);
+        sig = run_vm(fiber, in);
     }
 
     /* Restore */
     if (janet_vm_root_fiber == fiber) janet_vm_root_fiber = NULL;
-    janet_fiber_set_status(fiber, signal);
+    janet_fiber_set_status(fiber, sig);
     janet_restore(&tstate);
     fiber->last_value = tstate.payload;
     *out = tstate.payload;
 
-    return signal;
+    return sig;
 }
 
 /* Enter the main vm loop */
diff --git a/test/suite0010.janet b/test/suite0010.janet
index 752bbad2..fa83eba6 100644
--- a/test/suite0010.janet
+++ b/test/suite0010.janet
@@ -146,4 +146,18 @@
 # os/execute with environment variables
 (assert (= 0 (os/execute [(dyn :executable) "-e" "(+ 1 2 3)"] :pe {"HELLO" "WORLD"})) "os/execute with env")
 
+# Regression #638
+(assert
+  (= [true :caught]
+     (protect
+       (try
+         (do
+           (ev/sleep 0)
+           (with-dyns []
+             (ev/sleep 0)
+             (error "oops")))
+         ([err] :caught))))
+  "regression #638")
+
+
 (end-suite)