diff --git a/browser_patches/README.md b/browser_patches/README.md
index df28be78bf..0dbdd0523e 100644
--- a/browser_patches/README.md
+++ b/browser_patches/README.md
@@ -85,6 +85,10 @@ Set the `DEBUG=pw:browser` environment variable to see it.
 
 ## Firefox
 
+### Debug build
+
+When compiling set the `FF_DEBUG_BUILD=1` environment variable.
+
 #### Stack trace
 
 In `//mozglue/misc/StackWalk.cpp` add
@@ -96,7 +100,9 @@ In `//mozglue/misc/StackWalk.cpp` add
 In native code use
 
 ```c++
-nsTraceRefcnt::WalkTheStack(stderr);
+#include "mozilla/StackWalk.h"
+// ...
+MozWalkTheStack(stderr);
 ```
 
 If the stack trace is still mangled `cat` it to `tools/rb/fix_linux_stack.py`
diff --git a/browser_patches/firefox/build.sh b/browser_patches/firefox/build.sh
index 63915e1b4c..f3f1086bed 100755
--- a/browser_patches/firefox/build.sh
+++ b/browser_patches/firefox/build.sh
@@ -66,6 +66,10 @@ echo "mk_add_options MOZ_OBJDIR=@TOPSRCDIR@/${OBJ_FOLDER}" >> .mozconfig
 echo "ac_add_options --disable-crashreporter" >> .mozconfig
 echo "ac_add_options --disable-backgroundtasks" >> .mozconfig
 
+if [[ -n $FF_DEBUG_BUILD ]]; then
+  echo "ac_add_options --enable-debug" >> .mozconfig
+fi
+
 if [[ "$(uname)" == MINGW* || "$(uname)" == "Darwin" ]]; then
   # This options is only available on win and mac.
   echo "ac_add_options --disable-update-agent" >> .mozconfig
diff --git a/browser_patches/firefox/install-preferences.js b/browser_patches/firefox/install-preferences.js
index a1d850e14e..f82f791d54 100644
--- a/browser_patches/firefox/install-preferences.js
+++ b/browser_patches/firefox/install-preferences.js
@@ -31,7 +31,7 @@ async function installFirefoxPreferences(distpath) {
   if (os.platform() === 'linux')
     executablePath = path.join(distpath, 'firefox');
   else if (os.platform() === 'darwin')
-    executablePath = path.join(distpath, 'Nightly.app', 'Contents', 'MacOS', 'firefox');
+    executablePath = path.join(distpath, (process.env.FF_DEBUG_BUILD ? 'NightlyDebug.app' : 'Nightly.app'), 'Contents', 'MacOS', 'firefox');
   else if (os.platform() === 'win32')
     executablePath = path.join(distpath, 'firefox.exe');