diff --git a/unittest/force-styles/CMakeLists.txt b/unittest/force-styles/CMakeLists.txt
index dfffdfea0c..ac5cd7dfd7 100644
--- a/unittest/force-styles/CMakeLists.txt
+++ b/unittest/force-styles/CMakeLists.txt
@@ -199,6 +199,9 @@ add_executable(test_fix_timestep test_fix_timestep.cpp)
 if(NOT BUILD_SHARED_LIBS)
   target_compile_definitions(test_fix_timestep PRIVATE USING_STATIC_LIBS=1)
 endif()
+if(FFT_SINGLE)
+  target_compile_definitions(test_fix_timestep PRIVATE -DFFT_SINGLE)
+endif()
 target_link_libraries(test_fix_timestep PRIVATE lammps style_tests)
 
 # tests for timestep related fixes (time integration, thermostat, force manipulation, constraints/restraints)
diff --git a/unittest/force-styles/test_fix_timestep.cpp b/unittest/force-styles/test_fix_timestep.cpp
index d2e35b463f..b65eab2049 100644
--- a/unittest/force-styles/test_fix_timestep.cpp
+++ b/unittest/force-styles/test_fix_timestep.cpp
@@ -279,6 +279,10 @@ TEST(FixTimestep, plain)
     ASSERT_EQ(lmp->atom->natoms, nlocal);
 
     double epsilon = test_config.epsilon;
+    // relax test precision when using pppm and single precision FFTs
+#if defined(FFT_SINGLE)
+    if (lmp->force->kspace && utils::strmatch(lmp->force->kspace_style, "^pppm")) epsilon *= 2.0e8;
+#endif
 
     ErrorStats stats;
 
@@ -411,7 +415,6 @@ TEST(FixTimestep, plain)
     ifix = lmp->modify->find_fix("test");
     if (!utils::strmatch(lmp->modify->fix[ifix]->style, "^rigid") &&
         !utils::strmatch(lmp->modify->fix[ifix]->style, "^nve/limit")) {
-
         if (!verbose) ::testing::internal::CaptureStdout();
         cleanup_lammps(lmp, test_config);
         if (!verbose) ::testing::internal::GetCapturedStdout();
@@ -579,6 +582,10 @@ TEST(FixTimestep, omp)
     ASSERT_EQ(lmp->atom->natoms, nlocal);
 
     double epsilon = test_config.epsilon;
+    // relax test precision when using pppm and single precision FFTs
+#if defined(FFT_SINGLE)
+    if (lmp->force->kspace && utils::strmatch(lmp->force->kspace_style, "^pppm")) epsilon *= 2.0e8;
+#endif
 
     ErrorStats stats;