Index: clang-tidy/modernize/LoopConvertUtils.cpp
===================================================================
--- clang-tidy/modernize/LoopConvertUtils.cpp
+++ clang-tidy/modernize/LoopConvertUtils.cpp
@@ -819,6 +819,14 @@
   size_t Len = ContainerName.size();
   if (Len > 1 && ContainerName.endswith(Style == NS_UpperCase ? "S" : "s")) {
     IteratorName = ContainerName.substr(0, Len - 1);
+    // E.g.: (auto thing : things)
+    if (!declarationExists(IteratorName))
+      return IteratorName;
+  }
+
+  if (Len > 2 && ContainerName.endswith(Style == NS_UpperCase ? "S_" : "s_")) {
+    IteratorName = ContainerName.substr(0, Len - 2);
+    // E.g.: (auto thing : things_)
     if (!declarationExists(IteratorName))
       return IteratorName;
   }
@@ -835,14 +843,17 @@
   case NS_UpperCase:
     Elem = "ELEM";
   }
+  // E.g.: (auto elem : container)
   if (!declarationExists(Elem))
     return Elem;
 
   IteratorName = AppendWithStyle(ContainerName, OldIndex->getName());
+  // E.g.: (auto container_i : container)
   if (!declarationExists(IteratorName))
     return IteratorName;
 
   IteratorName = AppendWithStyle(ContainerName, Elem);
+  // E.g.: (auto container_elem : container)
   if (!declarationExists(IteratorName))
     return IteratorName;
 
Index: test/clang-tidy/modernize-loop-convert-lowercase.cpp
===================================================================
--- test/clang-tidy/modernize-loop-convert-lowercase.cpp
+++ test/clang-tidy/modernize-loop-convert-lowercase.cpp
@@ -7,6 +7,7 @@
 const int n = 10;
 int arr[n];
 int nums[n];
+int nums_[n];
 
 void naming() {
   for (int i = 0; i < n; ++i) {
@@ -23,6 +24,13 @@
   // CHECK-FIXES: for (auto & num : nums)
   // CHECK-FIXES-NEXT: printf("%d\n", num);
 
+  for (int i = 0; i < n; ++i) {
+    printf("%d\n", nums_[i]);
+  }
+  // CHECK-MESSAGES: :[[@LINE-3]]:3: warning: use range-based for loop instead
+  // CHECK-FIXES: for (auto & num : nums_)
+  // CHECK-FIXES-NEXT: printf("%d\n", num);
+
   int num = 0;
   for (int i = 0; i < n; ++i) {
     printf("%d\n", nums[i] + num);
Index: test/clang-tidy/modernize-loop-convert-uppercase.cpp
===================================================================
--- test/clang-tidy/modernize-loop-convert-uppercase.cpp
+++ test/clang-tidy/modernize-loop-convert-uppercase.cpp
@@ -7,6 +7,7 @@
 const int N = 10;
 int ARR[N];
 int NUMS[N];
+int NUMS_[N];
 
 void naming() {
   for (int I = 0; I < N; ++I) {
@@ -23,6 +24,13 @@
   // CHECK-FIXES: for (auto & NUM : NUMS)
   // CHECK-FIXES-NEXT: printf("%d\n", NUM);
 
+  for (int I = 0; I < N; ++I) {
+    printf("%d\n", NUMS_[I]);
+  }
+  // CHECK-MESSAGES: :[[@LINE-3]]:3: warning: use range-based for loop instead
+  // CHECK-FIXES: for (auto & NUM : NUMS_)
+  // CHECK-FIXES-NEXT: printf("%d\n", NUM);
+
   int NUM = 0;
   for (int I = 0; I < N; ++I) {
     printf("%d\n", NUMS[I] + NUM);