diff --git a/libs/full/collectives/tests/unit/all_gather.cpp b/libs/full/collectives/tests/unit/all_gather.cpp
index 099874a157b6..6227a6a8db03 100644
--- a/libs/full/collectives/tests/unit/all_gather.cpp
+++ b/libs/full/collectives/tests/unit/all_gather.cpp
@@ -21,7 +21,11 @@
 using namespace hpx::collectives;
 
 constexpr char const* all_gather_direct_basename = "/test/all_gather_direct/";
+#if defined(HPX_DEBUG)
+constexpr int ITERATIONS = 100;
+#else
 constexpr int ITERATIONS = 1000;
+#endif
 
 void test_one_shot_use()
 {
diff --git a/libs/full/collectives/tests/unit/all_reduce.cpp b/libs/full/collectives/tests/unit/all_reduce.cpp
index 011ae3ffebe7..551511d4b86d 100644
--- a/libs/full/collectives/tests/unit/all_reduce.cpp
+++ b/libs/full/collectives/tests/unit/all_reduce.cpp
@@ -21,7 +21,11 @@
 using namespace hpx::collectives;
 
 constexpr char const* all_reduce_direct_basename = "/test/all_reduce_direct/";
+#if defined(HPX_DEBUG)
+constexpr int ITERATIONS = 100;
+#else
 constexpr int ITERATIONS = 1000;
+#endif
 
 void test_one_shot_use()
 {
diff --git a/libs/full/collectives/tests/unit/all_to_all.cpp b/libs/full/collectives/tests/unit/all_to_all.cpp
index 4c9103a636f4..7a900094009f 100644
--- a/libs/full/collectives/tests/unit/all_to_all.cpp
+++ b/libs/full/collectives/tests/unit/all_to_all.cpp
@@ -21,7 +21,11 @@
 using namespace hpx::collectives;
 
 constexpr char const* all_to_all_direct_basename = "/test/all_to_all_direct/";
+#if defined(HPX_DEBUG)
+constexpr int ITERATIONS = 100;
+#else
 constexpr int ITERATIONS = 1000;
+#endif
 
 void test_one_shot_use()
 {
diff --git a/libs/full/collectives/tests/unit/broadcast.cpp b/libs/full/collectives/tests/unit/broadcast.cpp
index 6be90a530a16..92652ef4bd5c 100644
--- a/libs/full/collectives/tests/unit/broadcast.cpp
+++ b/libs/full/collectives/tests/unit/broadcast.cpp
@@ -21,7 +21,11 @@
 using namespace hpx::collectives;
 
 constexpr char const* broadcast_direct_basename = "/test/broadcast_direct/";
+#if defined(HPX_DEBUG)
+constexpr int ITERATIONS = 100;
+#else
 constexpr int ITERATIONS = 1000;
+#endif
 
 void test_one_shot_use()
 {
diff --git a/libs/full/collectives/tests/unit/exclusive_scan_.cpp b/libs/full/collectives/tests/unit/exclusive_scan_.cpp
index 75d3f90ea0e2..7aaa81cb8fb3 100644
--- a/libs/full/collectives/tests/unit/exclusive_scan_.cpp
+++ b/libs/full/collectives/tests/unit/exclusive_scan_.cpp
@@ -21,7 +21,11 @@
 using namespace hpx::collectives;
 
 constexpr char const* exclusive_scan_basename = "/test/exclusive_scan/";
+#if defined(HPX_DEBUG)
+constexpr int ITERATIONS = 100;
+#else
 constexpr int ITERATIONS = 1000;
+#endif
 
 void test_one_shot_use()
 {
diff --git a/libs/full/collectives/tests/unit/gather.cpp b/libs/full/collectives/tests/unit/gather.cpp
index 547c45d6201a..8de09c6412b4 100644
--- a/libs/full/collectives/tests/unit/gather.cpp
+++ b/libs/full/collectives/tests/unit/gather.cpp
@@ -21,7 +21,11 @@
 using namespace hpx::collectives;
 
 constexpr char const* gather_direct_basename = "/test/gather_direct/";
+#if defined(HPX_DEBUG)
+constexpr int ITERATIONS = 100;
+#else
 constexpr int ITERATIONS = 1000;
+#endif
 
 void test_one_shot_use()
 {
diff --git a/libs/full/collectives/tests/unit/inclusive_scan_.cpp b/libs/full/collectives/tests/unit/inclusive_scan_.cpp
index d60c5895c1c9..9ad8b0c26eb6 100644
--- a/libs/full/collectives/tests/unit/inclusive_scan_.cpp
+++ b/libs/full/collectives/tests/unit/inclusive_scan_.cpp
@@ -22,7 +22,11 @@
 using namespace hpx::collectives;
 
 constexpr char const* inclusive_scan_basename = "/test/inclusive_scan/";
+#if defined(HPX_DEBUG)
+constexpr int ITERATIONS = 100;
+#else
 constexpr int ITERATIONS = 1000;
+#endif
 
 void test_one_shot_use()
 {
diff --git a/libs/full/collectives/tests/unit/reduce.cpp b/libs/full/collectives/tests/unit/reduce.cpp
index 6940431dffc8..589e25e940a9 100644
--- a/libs/full/collectives/tests/unit/reduce.cpp
+++ b/libs/full/collectives/tests/unit/reduce.cpp
@@ -21,7 +21,11 @@
 using namespace hpx::collectives;
 
 constexpr char const* reduce_direct_basename = "/test/reduce_direct/";
+#if defined(HPX_DEBUG)
+constexpr int ITERATIONS = 100;
+#else
 constexpr int ITERATIONS = 1000;
+#endif
 
 void test_one_shot_use()
 {
diff --git a/libs/full/collectives/tests/unit/scatter.cpp b/libs/full/collectives/tests/unit/scatter.cpp
index d98ee090669d..4ad2f2a393eb 100644
--- a/libs/full/collectives/tests/unit/scatter.cpp
+++ b/libs/full/collectives/tests/unit/scatter.cpp
@@ -23,7 +23,11 @@
 using namespace hpx::collectives;
 
 constexpr char const* scatter_direct_basename = "/test/scatter_direct/";
+#if defined(HPX_DEBUG)
+constexpr int ITERATIONS = 100;
+#else
 constexpr int ITERATIONS = 1000;
+#endif
 
 void test_one_shot_use()
 {