diff --git a/src/libstore/gc.cc b/src/libstore/gc.cc
index 552016584a..b5cc21de44 100644
--- a/src/libstore/gc.cc
+++ b/src/libstore/gc.cc
@@ -482,7 +482,7 @@ void LocalStore::gcPath(const GCOptions & options, GCResults & results,
     results.bytesFreed += bytesFreed;
     results.blocksFreed += blocksFreed;
 
-    if (results.bytesFreed > options.maxFreed) {
+    if (options.maxFreed && results.bytesFreed > options.maxFreed) {
         printMsg(lvlInfo, format("deleted more than %1% bytes; stopping") % options.maxFreed);
         throw GCLimitReached();
     }
diff --git a/src/libstore/store-api.cc b/src/libstore/store-api.cc
index e80be1e68c..eb75d3ada1 100644
--- a/src/libstore/store-api.cc
+++ b/src/libstore/store-api.cc
@@ -5,12 +5,6 @@
 #include <limits.h>
 
 
-/* Needed for some ancient environments. */
-#ifndef ULLONG_MAX
-#define ULLONG_MAX 18446744073709551615ULL
-#endif
-
-
 namespace nix {
 
 
@@ -18,7 +12,7 @@ GCOptions::GCOptions()
 {
     action = gcDeleteDead;
     ignoreLiveness = false;
-    maxFreed = ULLONG_MAX;
+    maxFreed = 0;
     maxLinks = 0;
     useAtime = false;
     maxAtime = (time_t) -1;
diff --git a/src/libstore/store-api.hh b/src/libstore/store-api.hh
index 1c6f737285..bac2f6b9a2 100644
--- a/src/libstore/store-api.hh
+++ b/src/libstore/store-api.hh
@@ -56,7 +56,8 @@ struct GCOptions
     /* For `gcDeleteSpecific', the paths to delete. */
     PathSet pathsToDelete;
 
-    /* Stop after at least `maxFreed' bytes have been freed. */
+    /* Stop after at least `maxFreed' bytes have been freed.  0 means
+       no limit. */
     unsigned long long maxFreed;
 
     /* Stop after the number of hard links to the Nix store directory
diff --git a/src/nix-store/nix-store.cc b/src/nix-store/nix-store.cc
index 28cd1adf40..e842881379 100644
--- a/src/nix-store/nix-store.cc
+++ b/src/nix-store/nix-store.cc
@@ -531,7 +531,10 @@ static void opGC(Strings opFlags, Strings opArgs)
         else if (*i == "--print-live") options.action = GCOptions::gcReturnLive;
         else if (*i == "--print-dead") options.action = GCOptions::gcReturnDead;
         else if (*i == "--delete") options.action = GCOptions::gcDeleteDead;
-        else if (*i == "--max-freed") options.maxFreed = getIntArg(*i, i, opFlags.end());
+        else if (*i == "--max-freed") {
+            options.maxFreed = getIntArg(*i, i, opFlags.end());
+            if (options.maxFreed == 0) options.maxFreed = 1;
+        }
         else if (*i == "--max-links") options.maxLinks = getIntArg(*i, i, opFlags.end());
         else if (*i == "--use-atime") options.useAtime = true;
         else if (*i == "--max-atime") {