diff --git a/config/config.mk b/config/config.mk
index 67da9929e8f..d00b3f8b395 100644
--- a/config/config.mk
+++ b/config/config.mk
@@ -47,6 +47,7 @@ _MOZBUILD_EXTERNAL_VARIABLES := \
   GTEST_CPPSRCS \
   GTEST_CSRCS \
   HOST_CSRCS \
+  HOST_CMMSRCS \
   HOST_LIBRARY_NAME \
   IS_COMPONENT \
   JAVA_JAR_TARGETS \
diff --git a/js/src/config/config.mk b/js/src/config/config.mk
index 67da9929e8f..d00b3f8b395 100644
--- a/js/src/config/config.mk
+++ b/js/src/config/config.mk
@@ -47,6 +47,7 @@ _MOZBUILD_EXTERNAL_VARIABLES := \
   GTEST_CPPSRCS \
   GTEST_CSRCS \
   HOST_CSRCS \
+  HOST_CMMSRCS \
   HOST_LIBRARY_NAME \
   IS_COMPONENT \
   JAVA_JAR_TARGETS \
diff --git a/python/mozbuild/mozbuild/frontend/emitter.py b/python/mozbuild/mozbuild/frontend/emitter.py
index 7d24e86cf66..3b08fd94367 100644
--- a/python/mozbuild/mozbuild/frontend/emitter.py
+++ b/python/mozbuild/mozbuild/frontend/emitter.py
@@ -187,6 +187,7 @@ class TreeMetadataEmitter(LoggingMixin):
             },
             HOST_SOURCES={
                 '.c': 'HOST_CSRCS',
+                '.mm': 'HOST_CMMSRCS',
                 '.cc': 'HOST_CPPSRCS',
                 '.cpp': 'HOST_CPPSRCS',
             },
diff --git a/toolkit/crashreporter/google-breakpad/src/common/mac/Makefile.in b/toolkit/crashreporter/google-breakpad/src/common/mac/Makefile.in
index c02efdc408a..ca51a66b581 100644
--- a/toolkit/crashreporter/google-breakpad/src/common/mac/Makefile.in
+++ b/toolkit/crashreporter/google-breakpad/src/common/mac/Makefile.in
@@ -4,10 +4,6 @@
 
 LOCAL_INCLUDES 	= -I$(srcdir)/../..
 
-HOST_CMMSRCS = \
-  dump_syms.mm \
-  $(NULL)
-
 include $(topsrcdir)/config/rules.mk
 
 COMPILE_CMFLAGS += -std=c99
diff --git a/toolkit/crashreporter/google-breakpad/src/common/mac/moz.build b/toolkit/crashreporter/google-breakpad/src/common/mac/moz.build
index a26f33c25c7..9387edec5b1 100644
--- a/toolkit/crashreporter/google-breakpad/src/common/mac/moz.build
+++ b/toolkit/crashreporter/google-breakpad/src/common/mac/moz.build
@@ -22,6 +22,10 @@ SOURCES += [
 # crash reporter client.  Therefore, we don't need all the srcs in both.
 HOST_SOURCES += SOURCES
 
+HOST_SOURCES += [
+    'dump_syms.mm',
+]
+
 HOST_LIBRARY_NAME = 'host_breakpad_mac_common_s'
 SOURCES += [
     'HTTPMultipartUpload.m',
diff --git a/toolkit/crashreporter/google-breakpad/src/tools/mac/dump_syms/Makefile.in b/toolkit/crashreporter/google-breakpad/src/tools/mac/dump_syms/Makefile.in
index d62363170e7..75ea5426458 100644
--- a/toolkit/crashreporter/google-breakpad/src/tools/mac/dump_syms/Makefile.in
+++ b/toolkit/crashreporter/google-breakpad/src/tools/mac/dump_syms/Makefile.in
@@ -9,10 +9,6 @@ LOCAL_INCLUDES 	= \
   -I$(srcdir)/../../../common/mac \
   $(NULL)
 
-HOST_CMMSRCS = \
-  dump_syms_tool.mm \
-  $(NULL)
-
 HOST_LIBS += \
   $(DEPTH)/toolkit/crashreporter/google-breakpad/src/common/dwarf/$(LIB_PREFIX)host_breakpad_dwarf_s.$(LIB_SUFFIX) \
   $(DEPTH)/toolkit/crashreporter/google-breakpad/src/common/mac/$(LIB_PREFIX)host_breakpad_mac_common_s.$(LIB_SUFFIX) \
diff --git a/toolkit/crashreporter/google-breakpad/src/tools/mac/dump_syms/moz.build b/toolkit/crashreporter/google-breakpad/src/tools/mac/dump_syms/moz.build
index 895d11993cf..41f349c07ac 100644
--- a/toolkit/crashreporter/google-breakpad/src/tools/mac/dump_syms/moz.build
+++ b/toolkit/crashreporter/google-breakpad/src/tools/mac/dump_syms/moz.build
@@ -4,3 +4,6 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
+HOST_SOURCES += [
+    'dump_syms_tool.mm',
+]