diff --git a/Tools/ChangeLog b/Tools/ChangeLog
index 6680b8e..acf0b6e 100644
--- a/Tools/ChangeLog
+++ b/Tools/ChangeLog
@@ -1,3 +1,19 @@
+2020-01-15  David Kilzer  <ddkilzer@apple.com>
+
+        Enable -Wconditional-uninitialized in DumpRenderTree, WebKitTestRunner
+        <https://webkit.org/b/206269>
+        <rdar://problem/58589158>
+
+        Reviewed by Brent Fulgham.
+
+        * DumpRenderTree/mac/Configurations/Base.xcconfig:
+        (WARNING_CFLAGS): Add -Wconditional-uninitialized switch.
+        * DumpRenderTree/mac/UIDelegate.mm:
+        (-[UIDelegate webView:runOpenPanelForFileButtonWithResultListener:allowMultipleFiles:]):
+        Initialize `imageRef` stack variable to `nullptr`.
+        * WebKitTestRunner/Configurations/Base.xcconfig:
+        (WARNING_CFLAGS): Add -Wconditional-uninitialized switch.
+
 2020-01-15  Keith Miller  <keith_miller@apple.com>
 
         Revert bytecode checkpoints since it breaks watch
diff --git a/Tools/DumpRenderTree/mac/Configurations/Base.xcconfig b/Tools/DumpRenderTree/mac/Configurations/Base.xcconfig
index 1627936..55debb6 100644
--- a/Tools/DumpRenderTree/mac/Configurations/Base.xcconfig
+++ b/Tools/DumpRenderTree/mac/Configurations/Base.xcconfig
@@ -80,7 +80,7 @@
 // FIXME: <http://webkit.org/b/118590> DumpRenderTree should build with -Wshorten-64-to-32
 GCC_WARN_64_TO_32_BIT_CONVERSION[arch=arm64*] = NO;
 GCC_WARN_64_TO_32_BIT_CONVERSION[arch=x86_64] = NO;
-WARNING_CFLAGS = -Wall -W -Wno-unused-parameter -Wundef
+WARNING_CFLAGS = -Wall -W -Wconditional-uninitialized -Wno-unused-parameter -Wundef;
 
 DEBUG_DEFINES_debug = ;
 DEBUG_DEFINES_normal = NDEBUG;
diff --git a/Tools/DumpRenderTree/mac/UIDelegate.mm b/Tools/DumpRenderTree/mac/UIDelegate.mm
index 0634a9e..837b3c5 100644
--- a/Tools/DumpRenderTree/mac/UIDelegate.mm
+++ b/Tools/DumpRenderTree/mac/UIDelegate.mm
@@ -389,7 +389,7 @@
     NSURL *firstURL = [NSURL fileURLWithPath:[NSString stringWithUTF8String:openPanelFiles[0].c_str()] relativeToURL:baseURL];
     NSString *displayString = firstURL.lastPathComponent;
     const std::vector<char>& iconData = gTestRunner->openPanelFilesMediaIcon();
-    CGImageRef imageRef;
+    CGImageRef imageRef = nullptr;
     if (!iconData.empty()) {
         RetainPtr<CFDataRef> dataRef = adoptCF(CFDataCreate(nullptr, (unsigned char *)iconData.data(), iconData.size()));
         RetainPtr<CGDataProviderRef> imageProviderRef = adoptCF(CGDataProviderCreateWithCFData(dataRef.get()));
diff --git a/Tools/WebKitTestRunner/Configurations/Base.xcconfig b/Tools/WebKitTestRunner/Configurations/Base.xcconfig
index 85cb728..b531fd2 100644
--- a/Tools/WebKitTestRunner/Configurations/Base.xcconfig
+++ b/Tools/WebKitTestRunner/Configurations/Base.xcconfig
@@ -72,7 +72,7 @@
 GCC_WARN_UNUSED_VARIABLE = YES
 GCC_WARN_64_TO_32_BIT_CONVERSION[arch=arm64*] = NO;
 GCC_WARN_64_TO_32_BIT_CONVERSION[arch=x86_64] = NO;
-WARNING_CFLAGS = -Wall -W -Wno-unused-parameter -Wundef
+WARNING_CFLAGS = -Wall -W -Wconditional-uninitialized -Wno-unused-parameter -Wundef;
 GCC_PREFIX_HEADER = WebKitTestRunnerPrefix.h
 
 DEBUG_DEFINES_debug = ;