diff --git a/Misc/NEWS.d/next/Build/2021-12-02-13-17-57.bpo-40280.H4YNr5.rst b/Misc/NEWS.d/next/Build/2021-12-02-13-17-57.bpo-40280.H4YNr5.rst
new file mode 100644
index 00000000000000..70e75ada4a4220
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2021-12-02-13-17-57.bpo-40280.H4YNr5.rst
@@ -0,0 +1 @@
+Emscripten now builds with assertions enabled in debug builds.
\ No newline at end of file
diff --git a/configure b/configure
index 0aceffb35065a0..17852ab1653a2b 100755
--- a/configure
+++ b/configure
@@ -7521,6 +7521,12 @@ then
 	case $ac_sys_system in
 	    SCO_SV*) OPT="$OPT -m486 -DSCO5"
 	    ;;
+      Emscripten)
+        if test "$Py_DEBUG" = 'true' ; then
+          # Compile with assertions in debug mode
+          OPT="$OPT -s ASSERTIONS=1"
+        fi
+      ;;
         esac
 	;;
 
diff --git a/configure.ac b/configure.ac
index 99fa94d1029099..7d3a321603c2f2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1734,6 +1734,12 @@ then
 	case $ac_sys_system in
 	    SCO_SV*) OPT="$OPT -m486 -DSCO5"
 	    ;;
+      Emscripten)
+        if test "$Py_DEBUG" = 'true' ; then
+          # Compile with assertions in debug mode
+          OPT="$OPT -s ASSERTIONS=1"
+        fi
+      ;;
         esac
 	;;