diff --git a/src/libexpr/gc.cc b/src/libexpr/gc.cc
index 58107690d..1a56ac324 100644
--- a/src/libexpr/gc.cc
+++ b/src/libexpr/gc.cc
@@ -12,14 +12,14 @@ GC::GC()
     nextSize = std::max((size_t) 2, parseSize<size_t>(getEnv("GC_INITIAL_HEAP_SIZE", "131072")) / WORD_SIZE);
 
     // FIXME: placement new
-    frontSentinel = (Ptr<Object> *) malloc(sizeof(Ptr<Object>));
-    backSentinel = (Ptr<Object> *) malloc(sizeof(Ptr<Object>));
+    frontPtrSentinel = (Ptr<Object> *) malloc(sizeof(Ptr<Object>));
+    backPtrSentinel = (Ptr<Object> *) malloc(sizeof(Ptr<Object>));
 
-    frontSentinel->prev = nullptr;
-    frontSentinel->next = backSentinel;
+    frontPtrSentinel->prev = nullptr;
+    frontPtrSentinel->next = backPtrSentinel;
 
-    backSentinel->prev = frontSentinel;
-    backSentinel->next = nullptr;
+    backPtrSentinel->prev = frontPtrSentinel;
+    backPtrSentinel->next = nullptr;
 
     frontRootSentinel = (Root<Object> *) malloc(sizeof(Root<Object>));
     backRootSentinel = (Root<Object> *) malloc(sizeof(Root<Object>));
@@ -47,7 +47,7 @@ GC::~GC()
     debug("allocated %d bytes in total", totalSize * WORD_SIZE);
 
     size_t n = 0;
-    for (Ptr<Object> * p = frontSentinel->next; p != backSentinel; p = p->next)
+    for (Ptr<Object> * p = frontPtrSentinel->next; p != backPtrSentinel; p = p->next)
         n++;
     if (n)
         warn("%d GC root pointers still exist on exit", n);
@@ -58,8 +58,8 @@ GC::~GC()
     if (n)
         warn("%d GC root objects still exist on exit", n);
 
-    assert(!frontSentinel->prev);
-    assert(!backSentinel->next);
+    assert(!frontPtrSentinel->prev);
+    assert(!backPtrSentinel->next);
     assert(!frontRootSentinel->prev);
     assert(!backRootSentinel->next);
 }
@@ -227,7 +227,7 @@ void GC::gc()
         processStack();
     }
 
-    for (Ptr<Object> * p = frontSentinel->next; p != backSentinel; p = p->next) {
+    for (Ptr<Object> * p = frontPtrSentinel->next; p != backPtrSentinel; p = p->next) {
         if (!p->value) continue;
         stack.push(p->value);
         processStack();
diff --git a/src/libexpr/gc.hh b/src/libexpr/gc.hh
index f8be832eb..5a62fb052 100644
--- a/src/libexpr/gc.hh
+++ b/src/libexpr/gc.hh
@@ -136,8 +136,8 @@ struct GC
 
 private:
 
-    Ptr<Object> * frontSentinel;
-    Ptr<Object> * backSentinel;
+    Ptr<Object> * frontPtrSentinel;
+    Ptr<Object> * backPtrSentinel;
 
     Root<Object> * frontRootSentinel;
     Root<Object> * backRootSentinel;
@@ -295,7 +295,7 @@ private:
 
     void link()
     {
-        prev = (Ptr *) gc.frontSentinel;
+        prev = (Ptr *) gc.frontPtrSentinel;
         next = prev->next;
         next->prev = this;
         prev->next = this;