diff --git a/bin/build-src-distrib.sh b/bin/build-src-distrib.sh
index 193d6ed9a4614894d5d7daecf0c3ee4fbaf9db5c..d60f1e1b1b48013f55a3facbfca08bbfa065a250 100755
--- a/bin/build-src-distrib.sh
+++ b/bin/build-src-distrib.sh
@@ -14,19 +14,19 @@ DEBUG=no
 # (special use of the 'case' construct)
 if test `echo $BASH_VERSION | sed "s/\([0-9]\).*/\1/" ` -lt 4; then
     echo "bash version >= 4 is required."
-    exit 99
+    exit 127
 fi
 
 # git-lfs needs to be installed
 if ! command -v git-lfs >/dev/null 2>/dev/null; then
     echo "git-lfs is required"
-    exit 99
+    exit 127
 fi
 
 # grep needs to be installed
 if ! command -v grep --version >/dev/null 2>/dev/null; then
     echo "grep is required"
-    exit 99
+    exit 127
 fi
 
 function run {
diff --git a/doc/build-manuals.sh b/doc/build-manuals.sh
index 353f2a43d2922800c2c49054163491b92f712242..b4b808f959ad1b458ba7649c47ebd77ca0c57f91 100755
--- a/doc/build-manuals.sh
+++ b/doc/build-manuals.sh
@@ -1,5 +1,17 @@
 #! /usr/bin/env bash
 
+# GNU parallel needs to be installed
+if ! command -v parallel >/dev/null 2>/dev/null; then
+    echo "parallel is required"
+    exit 127
+fi
+
+# latexmk needs to be installed
+if ! command -v latexmk >/dev/null 2>/dev/null; then
+    echo "latexmk is required"
+    exit 127
+fi
+
 cd $(dirname $0)
 
 usage () {
@@ -20,7 +32,7 @@ fi
 set -e
 
 if [ ! -e acsl ]; then
-    echo "error: 'acsl' not in doc; clone git@github.com:acsl-language/acsl.git"
+    echo "error: 'acsl' not in doc; try: git clone git@github.com:acsl-language/acsl.git"
     exit 1
 fi
 
@@ -32,7 +44,7 @@ ACSL_SUFFIX=$(grep acslversion acsl/version.tex | sed 's/.*{\([^{}\\]*\).*/\1/')
 EACSL_SUFFIX=$(grep 'newcommand{\\eacsllangversion' ../src/plugins/e-acsl/doc/refman/main.tex | sed 's/.*{\([^{}\\]*\).*/\1/')
 # sanity check
 if [ "$EACSL_SUFFIX" = "" ]; then
-    echo "error: could not retrive E-ACSL version from ../src/plugins/e-acsl/doc/refman/main.tex"
+    echo "error: could not retrieve E-ACSL version from ../src/plugins/e-acsl/doc/refman/main.tex"
     exit 1
 fi