diff --git a/bash-env-json b/bash-env-json
index 3ac7cc8..374bb32 100755
--- a/bash-env-json
+++ b/bash-env-json
@@ -129,9 +129,9 @@ function eval_or_source() {
     _path="$1"
 
     _error_file=$(mktemp -u)
-    # tell ShellCheck I really do want to expand this now and not at the point of exit
-    # shellcheck disable=SC2064
-    trap "rm -f $_error_file" EXIT
+    touch "$_error_file"
+    exec 3<"$_error_file" 4>"$_error_file"
+    rm -f "$_error_file"
 
     if test -n "$_path"; then
         # source from file if specified
@@ -142,19 +142,35 @@ function eval_or_source() {
 
         # ShellCheck can't cope with sourcing from an unknown path
         # shellcheck disable=SC1090
-        if ! source "$_path" >/dev/null 2>"$_error_file"; then
-            emit_error_exit "$(head -1 "$_error_file")"
+        if ! source "$_path" >/dev/null 2>&4; then
+            exec 4>&-
+            emit_error_exit "$(head -1 <&3)"
         fi
     else
         # otherwise eval from stdin
         _source=$(</dev/stdin)
-        if ! eval "$_source" >/dev/null 2>"$_error_file"; then
+        if ! eval "$_source" >/dev/null 2>&4; then
+            exec 4>&-
             # discard error location, because it is this file not the one sourced
-            emit_error_exit "$(sed -e 's/^.*line\s*[0-9]*:\s*//' "$_error_file")"
+            emit_error_exit "$(sed -e 's/^.*line\s*[0-9]*:\s*//' <&3)"
         fi
     fi
 }
 
+function invoke_safely() {
+    local _fn="$1"
+
+    _error_file=$(mktemp -u)
+    touch "$_error_file"
+    exec 3<"$_error_file" 4>"$_error_file"
+    rm -f "$_error_file"
+
+    "$_fn" >/dev/null 2>&4 || {
+        exec 4>&-
+        emit_error_exit "$(head -1 <&3)"
+    }
+}
+
 function get_args() {
     local -n _opt_path="$1"
     local -n _opt_shellfn_names="$2"
@@ -203,39 +219,40 @@ function main() {
     eval_or_source "$_path"
     capture _env_current _shellvars_current
 
-    # validate all the functions we will invoke before committing to the happy path
-    for _fn in "${_shellfn_names[@]}"; do
-        test "$(type -t "$_fn")" == "function" || {
-            emit_error_exit "no such function: $_fn"
-        }
-    done
+    # accumulate result in a file until we know we are error-free
+    _result_file=$(mktemp -u)
+    touch "$_result_file"
+    exec 5<"$_result_file" 6>"$_result_file"
+    rm -f "$_result_file"
 
-    emit "{" env _env_previous _env_current
-    emit "," shellvars _shellvars_previous _shellvars_current
+    emit "{" env _env_previous _env_current >&6
+    emit "," shellvars _shellvars_previous _shellvars_current >&6
 
     test "${#_shellfn_names[@]}" -gt 0 && {
-        echo ",\"fn\":{"
+        echo ",\"fn\":{" >&6
     }
 
     local _fn_comma=""
     for _fn in "${_shellfn_names[@]}"; do
         capture _env_previous _shellvars_previous
-        # execute the function
-        "$_fn"
+        invoke_safely "$_fn"
         capture _env_current _shellvars_current
 
-        echo "$_fn_comma\"$_fn\":"
-        emit "{" env _env_previous _env_current
-        emit "," shellvars _shellvars_previous _shellvars_current
-        echo "}"
+        echo "$_fn_comma\"$_fn\":" >&6
+        emit "{" env _env_previous _env_current >&6
+        emit "," shellvars _shellvars_previous _shellvars_current >&6
+        echo "}" >&6
         _fn_comma=","
     done
 
     test "${#_shellfn_names[@]}" -gt 0 && {
-        echo "}"
+        echo "}" >&6
     }
 
-    echo "}"
+    echo "}" >&6
+    exec 6>&-
+
+    cat <&5
 }
 
 function bad_usage() {
diff --git a/tests/shell-function-error.env b/tests/shell-function-error.env
new file mode 100644
index 0000000..60c9696
--- /dev/null
+++ b/tests/shell-function-error.env
@@ -0,0 +1,3 @@
+function f() {
+	whacky-doodle-doo
+}