diff --git a/pkgs/by-name/sp/speech-tools/fix-unbonded-variable.patch b/pkgs/by-name/sp/speech-tools/fix-unbonded-variable.patch
new file mode 100644
index 000000000000..4b63d05b69b8
--- /dev/null
+++ b/pkgs/by-name/sp/speech-tools/fix-unbonded-variable.patch
@@ -0,0 +1,39 @@
+diff --git a/scripts/est_examples.sh b/scripts/est_examples.sh
+index 5e6f38c..b931fda 100755
+--- a/scripts/est_examples.sh
++++ b/scripts/est_examples.sh
+@@ -64,7 +64,7 @@ EOF
+ prepend() {
+ 	var="$1"
+ 	extra="$2"
+-	eval "val=\$$var"
++	eval "val=\${$var:-}"
+ 	
+ 	if [ -n "$val" ]
+ 		then
+diff --git a/scripts/shared_script b/scripts/shared_script
+index b159134..2732699 100644
+--- a/scripts/shared_script
++++ b/scripts/shared_script
+@@ -5,7 +5,7 @@
+ extend() {
+ 	var="$1"
+ 	extra="$2"
+-	eval "val=\$$var"
++	eval "val=\${$var:-}"
+ 	
+ 	if [ -n "$val" ]
+ 		then
+diff --git a/scripts/shared_setup_sh b/scripts/shared_setup_sh
+index 64f0ba9..e0488f4 100644
+--- a/scripts/shared_setup_sh
++++ b/scripts/shared_setup_sh
+@@ -4,7 +4,7 @@
+ extend() {
+ 	var="$1"
+ 	extra="$2"
+-	eval "val=\$$var"
++	eval "val=\${$var:-}"
+ 	
+ 	if [ -n "$val" ]
+ 		then
diff --git a/pkgs/by-name/sp/speech-tools/package.nix b/pkgs/by-name/sp/speech-tools/package.nix
index 44cad0adedae..7d55117771d7 100644
--- a/pkgs/by-name/sp/speech-tools/package.nix
+++ b/pkgs/by-name/sp/speech-tools/package.nix
@@ -5,6 +5,7 @@
   fetchpatch,
   ncurses,
   alsa-lib,
+  perl,
 }:
 
 stdenv.mkDerivation (finalAttrs: {
@@ -24,10 +25,13 @@ stdenv.mkDerivation (finalAttrs: {
     })
     # Fix C23 compatibility: https://github.com/festvox/speech_tools/pull/58
     ./fix-c23.patch
+    # Fix "unbonded variable" error in some scripts
+    ./fix-unbonded-variable.patch
   ];
 
   buildInputs = [
     ncurses
+    perl
   ]
   ++ lib.optionals stdenv.hostPlatform.isLinux [
     alsa-lib
@@ -50,11 +54,16 @@ stdenv.mkDerivation (finalAttrs: {
     # c99 makes isnan valid for float and double
     substituteInPlace include/EST_math.h \
       --replace '__isnanf(X)' 'isnan(X)'
+
+    # fix script referenced paths
+    substituteInPlace config/rules/script_process.awk \
+      --replace-fail "topdir" "\"$out\"" \
+      --replace-fail "est" "\"$out\""
   '';
 
   installPhase = ''
-    mkdir -p "$out"/{bin,lib}
-    for d in bin lib; do
+    mkdir -p "$out"/{bin,include,lib}
+    for d in bin include lib; do
       for i in ./$d/*; do
         test "$(basename "$i")" = "Makefile" ||
           cp -r "$(readlink -f $i)" "$out/$d"