diff --git a/browser/components/shell/nsWindowsShellService.cpp b/browser/components/shell/nsWindowsShellService.cpp
index e3c4aa5bcb6b..1f4bcf1dc1db 100644
--- a/browser/components/shell/nsWindowsShellService.cpp
+++ b/browser/components/shell/nsWindowsShellService.cpp
@@ -805,7 +805,7 @@ static nsresult CreateShortcutImpl(
   // TODO: Properly escape quotes in the string, see bug 1604287.
   nsString arguments;
   for (auto& arg : aArguments) {
-    arguments.AppendPrintf("\"%S\" ", arg.get());
+    arguments.AppendPrintf("\"%S\" ", static_cast<const wchar_t*>(arg.get()));
   }
 
   link->SetArguments(arguments.get());
diff --git a/extensions/auth/nsAuthSSPI.cpp b/extensions/auth/nsAuthSSPI.cpp
index ffc500a994bb..3c051d34bfdb 100644
--- a/extensions/auth/nsAuthSSPI.cpp
+++ b/extensions/auth/nsAuthSSPI.cpp
@@ -221,7 +221,7 @@ nsAuthSSPI::Init(const nsACString& aServiceName, uint32_t aServiceFlags,
   PSecPkgInfoW pinfo;
   rc = (sspi->QuerySecurityPackageInfoW)(package, &pinfo);
   if (rc != SEC_E_OK) {
-    LOG(("%s package not found\n", package));
+    LOG(("%S package not found\n", package));
     return NS_ERROR_UNEXPECTED;
   }
   mMaxTokenLen = pinfo->cbMaxToken;
diff --git a/security/manager/ssl/nsNSSComponent.cpp b/security/manager/ssl/nsNSSComponent.cpp
index b2b076c01c1e..89353386e0ec 100644
--- a/security/manager/ssl/nsNSSComponent.cpp
+++ b/security/manager/ssl/nsNSSComponent.cpp
@@ -469,7 +469,8 @@ static nsresult AccountHasFamilySafetyEnabled(bool& enabled) {
     MOZ_LOG(gPIPNSSLog, LogLevel::Debug, ("couldn't get sid"));
     return NS_ERROR_FAILURE;
   }
-  MOZ_LOG(gPIPNSSLog, LogLevel::Debug, ("our sid is '%S'", sid.get()));
+  MOZ_LOG(gPIPNSSLog, LogLevel::Debug,
+          ("our sid is '%S'", static_cast<const wchar_t*>(sid.get())));
   bool hasSid;
   rv = usersKey->HasChild(sid, &hasSid);
   if (NS_FAILED(rv)) {
diff --git a/security/sandbox/win/src/sandboxbroker/sandboxBroker.cpp b/security/sandbox/win/src/sandboxbroker/sandboxBroker.cpp
index 0e08b7ca22a1..c62f1a7f13c9 100644
--- a/security/sandbox/win/src/sandboxbroker/sandboxBroker.cpp
+++ b/security/sandbox/win/src/sandboxbroker/sandboxBroker.cpp
@@ -406,7 +406,7 @@ static void AddCachedDirRule(sandbox::TargetPolicy* aPolicy,
     // This can only be an NS_WARNING, because it can null for xpcshell tests.
     NS_WARNING("Tried to add rule with null base dir.");
     LOG_E("Tried to add rule with null base dir. Relative path: %S, Access: %d",
-          aRelativePath.get(), aAccess);
+          static_cast<const wchar_t*>(aRelativePath.get()), aAccess);
     return;
   }
 
@@ -418,7 +418,7 @@ static void AddCachedDirRule(sandbox::TargetPolicy* aPolicy,
   if (sandbox::SBOX_ALL_OK != result) {
     NS_ERROR("Failed to add file policy rule.");
     LOG_E("Failed (ResultCode %d) to add %d access to: %S", result, aAccess,
-          rulePath.get());
+          static_cast<const wchar_t*>(rulePath.get()));
   }
 }
 
diff --git a/toolkit/components/remote/RemoteUtils.h b/toolkit/components/remote/RemoteUtils.h
index e8ff64a39df5..9f3557102f3c 100644
--- a/toolkit/components/remote/RemoteUtils.h
+++ b/toolkit/components/remote/RemoteUtils.h
@@ -18,7 +18,7 @@ static void BuildClassName(const char* aProgram, const char* aProfile,
 #  if defined XP_WIN
   nsString pfn = mozilla::widget::WinUtils::GetPackageFamilyName();
   if (!pfn.IsEmpty()) {
-    aClassName.AppendPrintf("_%s", pfn.get());
+    aClassName.AppendPrintf("_%S", static_cast<const wchar_t*>(pfn.get()));
   }
 #  endif
   aClassName.AppendPrintf("_%s_RemoteWindow", aProfile);
diff --git a/uriloader/exthandler/win/nsOSHelperAppService.cpp b/uriloader/exthandler/win/nsOSHelperAppService.cpp
index ef9b6340099e..f93d87658004 100644
--- a/uriloader/exthandler/win/nsOSHelperAppService.cpp
+++ b/uriloader/exthandler/win/nsOSHelperAppService.cpp
@@ -444,8 +444,8 @@ nsOSHelperAppService::GetMIMEInfoFromOS(const nsACString& aMIMEType,
   bool haveMeaningfulMimeType =
       !aMIMEType.IsEmpty() &&
       !aMIMEType.LowerCaseEqualsLiteral(APPLICATION_OCTET_STREAM);
-  LOG(("Extension lookup on '%s' with mimetype '%s'%s\n", fileExtension.get(),
-       flatType.get(),
+  LOG(("Extension lookup on '%S' with mimetype '%s'%s\n",
+       static_cast<const wchar_t*>(fileExtension.get()), flatType.get(),
        haveMeaningfulMimeType ? " (treated as meaningful)" : ""));
 
   RefPtr<nsMIMEInfoWin> mi;
@@ -477,14 +477,14 @@ nsOSHelperAppService::GetMIMEInfoFromOS(const nsACString& aMIMEType,
        !typeFromExtEquals(fileExtension.get(), flatType.get()))) {
     usedMimeTypeExtensionForLookup = true;
     fileExtension = extensionFromMimeType;
-    LOG(("Now using '%s' mimetype's default file extension '%s' for lookup\n",
-         flatType.get(), fileExtension.get()));
+    LOG(("Now using '%s' mimetype's default file extension '%S' for lookup\n",
+         flatType.get(), static_cast<const wchar_t*>(fileExtension.get())));
   }
 
   // If we have an extension, use it for lookup:
   mi = GetByExtension(fileExtension, flatType.get());
-  LOG(("Extension lookup on '%s' found: 0x%p\n", fileExtension.get(),
-       mi.get()));
+  LOG(("Extension lookup on '%S' found: 0x%p\n",
+       static_cast<const wchar_t*>(fileExtension.get()), mi.get()));
 
   if (mi) {
     bool hasDefault = false;
@@ -494,8 +494,9 @@ nsOSHelperAppService::GetMIMEInfoFromOS(const nsACString& aMIMEType,
     if (!hasDefault && !usedMimeTypeExtensionForLookup) {
       RefPtr<nsMIMEInfoWin> miFromMimeType =
           GetByExtension(extensionFromMimeType, flatType.get());
-      LOG(("Mime-based ext. lookup for '%s' found 0x%p\n",
-           extensionFromMimeType.get(), miFromMimeType.get()));
+      LOG(("Mime-based ext. lookup for '%S' found 0x%p\n",
+           static_cast<const wchar_t*>(extensionFromMimeType.get()),
+           miFromMimeType.get()));
       if (miFromMimeType) {
         nsAutoString desc;
         miFromMimeType->GetDefaultDescription(desc);
@@ -510,8 +511,8 @@ nsOSHelperAppService::GetMIMEInfoFromOS(const nsACString& aMIMEType,
   // different:
   if (!extensionFromMimeType.IsEmpty() && !usedMimeTypeExtensionForLookup) {
     mi = GetByExtension(extensionFromMimeType, flatType.get());
-    LOG(("Mime-based ext. lookup for '%s' found 0x%p\n",
-         extensionFromMimeType.get(), mi.get()));
+    LOG(("Mime-based ext. lookup for '%S' found 0x%p\n",
+         static_cast<const wchar_t*>(extensionFromMimeType.get()), mi.get()));
   }
   if (mi) {
     mi.forget(aMIMEInfo);
diff --git a/widget/windows/GfxInfo.cpp b/widget/windows/GfxInfo.cpp
index b17c1e21c040..ddbae100c62e 100644
--- a/widget/windows/GfxInfo.cpp
+++ b/widget/windows/GfxInfo.cpp
@@ -124,7 +124,8 @@ GfxInfo::GetCleartypeParameters(nsAString& aCleartypeParams) {
     ClearTypeParameterInfo& params = clearTypeParams[d];
 
     if (displayNames) {
-      outStr.AppendPrintf("%S [ ", params.displayName.get());
+      outStr.AppendPrintf(
+          "%S [ ", static_cast<const wchar_t*>(params.displayName.get()));
     }
 
     if (params.gamma >= 0) {
@@ -137,8 +138,8 @@ GfxInfo::GetCleartypeParameters(nsAString& aCleartypeParams) {
       if (params.pixelStructure == PIXEL_STRUCT_RGB ||
           params.pixelStructure == PIXEL_STRUCT_BGR) {
         outStr.AppendPrintf(
-            "Pixel Structure: %S ",
-            (params.pixelStructure == PIXEL_STRUCT_RGB ? u"RGB" : u"BGR"));
+            "Pixel Structure: %s ",
+            (params.pixelStructure == PIXEL_STRUCT_RGB ? "RGB" : "BGR"));
       } else {
         outStr.AppendPrintf("Pixel Structure: %d ", params.pixelStructure);
       }