diff --git a/accumulate.hpp b/accumulate.hpp
index 0d43a20e..fb29853d 100644
--- a/accumulate.hpp
+++ b/accumulate.hpp
@@ -61,7 +61,7 @@ class iter::impl::Accumulator {
           sub_end_{std::move(sub_end)},
           accumulate_func_(&accumulate_fun),
           // only get first value if not an end iterator
-          acc_val_{!(sub_iter_ != sub_end_)
+          acc_val_{(sub_iter_ == sub_end_)
                        ? std::nullopt
                        : std::make_optional<AccumVal>(*sub_iter_)} {}
 
diff --git a/batched.hpp b/batched.hpp
index e5eadf13..1f198254 100644
--- a/batched.hpp
+++ b/batched.hpp
@@ -129,7 +129,7 @@ class iter::impl::Batcher {
     template <typename T>
     bool operator==(const Iterator<T>& other) const {
       return done() == other.done()
-             && (done() || !(sub_iter_ != other.sub_iter_));
+             && (done() || (sub_iter_ == other.sub_iter_));
     }
 
     DerefVec<ContainerT>& operator*() {
diff --git a/chunked.hpp b/chunked.hpp
index 1d03b6e1..b1ae1c83 100644
--- a/chunked.hpp
+++ b/chunked.hpp
@@ -101,7 +101,7 @@ class iter::impl::Chunker {
     template <typename T>
     bool operator==(const Iterator<T>& other) const {
       return done() == other.done()
-             && (done() || !(sub_iter_ != other.sub_iter_));
+             && (done() || (sub_iter_ == other.sub_iter_));
     }
 
     DerefVec<ContainerT>& operator*() {
diff --git a/cycle.hpp b/cycle.hpp
index 1d3ecaef..2fb0c0ce 100644
--- a/cycle.hpp
+++ b/cycle.hpp
@@ -63,7 +63,7 @@ class iter::impl::Cycler {
     Iterator& operator++() {
       ++sub_iter_;
       // reset to beginning upon reaching the sub_end_
-      if (!(sub_iter_ != sub_end_)) {
+      if ((sub_iter_ == sub_end_)) {
         sub_iter_ = sub_begin_;
       }
       return *this;
diff --git a/groupby.hpp b/groupby.hpp
index 4f2fffb5..bd780305 100644
--- a/groupby.hpp
+++ b/groupby.hpp
@@ -154,7 +154,7 @@ class iter::impl::GroupProducer {
     }
 
     bool exhausted() const {
-      return !(sub_iter_ != sub_end_);
+      return (sub_iter_ == sub_end_);
     }
 
     typename Holder<ContainerT>::reference get() {
diff --git a/test/test_iteratoriterator.cpp b/test/test_iteratoriterator.cpp
index dd2c4987..d69e4dd5 100644
--- a/test/test_iteratoriterator.cpp
+++ b/test/test_iteratoriterator.cpp
@@ -85,26 +85,25 @@ TEST_CASE("IteratorIterator supports mutable RandomAccessIterator operators",
   REQUIRE(&(*r2++) == &a[1]);
   REQUIRE(r == r2);
   auto test_const_or_not = [&itr](auto& a, auto& b) {
-    REQUIRE(!(b == a));
+    REQUIRE((b != a));
     REQUIRE(b == a + 2);
     REQUIRE(b == 2 + a);
     REQUIRE(b - 2 == a);
     REQUIRE(&a[2] == &b[0]);
     REQUIRE(b - a == 2);
     REQUIRE(a < b);
-    REQUIRE(!(a < a));
+    REQUIRE((a >= a));
     REQUIRE(b > a);
-    REQUIRE(!(a > a));
+    REQUIRE((a = a));
     REQUIRE(a <= b);
-    REQUIRE(!(b <= a));
+    REQUIRE((b > a));
     REQUIRE(a <= a);
     REQUIRE(b >= a);
-    REQUIRE(!(a >= b));
+    REQUIRE((a < b));
     REQUIRE(a >= a);
 
     // InputIterator:
     REQUIRE(b != a);
-    REQUIRE(!(a != a));
     REQUIRE(&(*a) != &(*b));
     REQUIRE(&(a->value) == &(*a).value);