diff --git a/src/sfizz/FilePool.cpp b/src/sfizz/FilePool.cpp
index d711e9c5..f3e73dd1 100644
--- a/src/sfizz/FilePool.cpp
+++ b/src/sfizz/FilePool.cpp
@@ -289,17 +289,17 @@ void sfz::FilePool::cleanupPromises() noexcept
     // The garbage collection cleared the data from these so we can move them
     // back to the empty queue
     auto clearedIterator = promisesToClear.begin();
-    auto clearedSentinel = promisesToClear.end() - 1;
-    while (clearedIterator != promisesToClear.end()) {
+    auto clearedSentinel = promisesToClear.rbegin();
+    while (clearedIterator < clearedSentinel.base()) {
         if (clearedIterator->get()->dataReady == false) {
             emptyPromises.push_back(*clearedIterator);
             std::iter_swap(clearedIterator, clearedSentinel);
-            clearedSentinel--;
-            promisesToClear.pop_back();
+            ++clearedSentinel;
         } else {
-            clearedIterator++;
+            ++clearedIterator;
         }
     }
+    promisesToClear.resize(std::distance(promisesToClear.begin(), clearedSentinel.base()));
 
     FilePromisePtr promise;
     // Remove the promises from the filled queue and put them in a linear
@@ -308,17 +308,17 @@ void sfz::FilePool::cleanupPromises() noexcept
         temporaryFilePromises.push_back(promise);
 
     auto filledIterator = temporaryFilePromises.begin();
-    auto filledSentinel = temporaryFilePromises.end() - 1;
-    while (filledIterator != temporaryFilePromises.end()) {
+    auto filledSentinel = temporaryFilePromises.rbegin();
+    while (filledIterator < filledSentinel.base()) {
         if (filledIterator->use_count() == 1) {
             promisesToClear.push_back(*filledIterator);
             std::iter_swap(filledIterator, filledSentinel);
-            filledSentinel--;
-            temporaryFilePromises.pop_back();
+            ++filledSentinel;
         } else {
-            filledIterator++;
+            ++filledIterator;
         }
     }
+    temporaryFilePromises.resize(std::distance(temporaryFilePromises.begin(), filledSentinel.base()));
 }
 
 void sfz::FilePool::setOversamplingFactor(sfz::Oversampling factor) noexcept
diff --git a/src/sfizz/Synth.cpp b/src/sfizz/Synth.cpp
index 511e94c7..4d888366 100644
--- a/src/sfizz/Synth.cpp
+++ b/src/sfizz/Synth.cpp
@@ -237,9 +237,9 @@ bool sfz::Synth::loadSfzFile(const fs::path& filename)
 
     resources.filePool.setRootDirectory(this->originalDirectory);
 
-    auto lastRegion = regions.end() - 1;
     auto currentRegion = regions.begin();
-    while (currentRegion <= lastRegion) {
+    auto lastRegion = regions.rbegin();
+    while (currentRegion < lastRegion.base()) {
         auto region = currentRegion->get();
 
         if (!region->isGenerator()) {
@@ -247,7 +247,7 @@ bool sfz::Synth::loadSfzFile(const fs::path& filename)
             if (!fileInformation) {
                 DBG("Removing the region with sample " << region->sample);
                 std::iter_swap(currentRegion, lastRegion);
-                lastRegion--;
+                ++lastRegion;
                 continue;
             }
             region->sampleEnd = std::min(region->sampleEnd, fileInformation->end);
@@ -298,11 +298,11 @@ bool sfz::Synth::loadSfzFile(const fs::path& filename)
         region->registerAftertouch(0);
         region->registerTempo(2.0f);
 
-        currentRegion++;
+        ++currentRegion;
     }
-
-    DBG("Removed " << regions.size() - std::distance(regions.begin(), lastRegion) - 1 << " out of " << regions.size() << " regions.");
-    regions.resize(std::distance(regions.begin(), lastRegion) + 1);
+    const auto remainingRegions = std::distance(regions.begin(), lastRegion.base());
+    DBG("Removing " << (regions.size() - remainingRegions) << " out of " << regions.size() << " regions");
+    regions.resize(remainingRegions);
     modificationTime = checkModificationTime();
 
     return parserReturned;