diff --git a/unit_tests/testIndividual.cpp b/unit_tests/testIndividual.cpp
index 5c526ea..4ced6fd 100644
--- a/unit_tests/testIndividual.cpp
+++ b/unit_tests/testIndividual.cpp
@@ -571,42 +571,83 @@ void testGenetics() {
 
 	// Genetic fitness mutations are constrained between -1 or 1
 	{
-		// Most likely (~96%) to sample a mutation > 1
-		const float gammaMutShapeParam = 5.0;
-		const float gammaMutScaleParam = 1.0;
+		{
+			// Most likely (~96%) to sample a mutation > 1
+			const float gammaMutShapeParam = 5.0;
+			const float gammaMutScaleParam = 1.0;
 
-		const int genomeSz = 5;
-		const bool isDiploid{ false };
+			const int genomeSz = 5;
+			const bool isDiploid{ false };
 
-		// Create species trait
-		const map<GenParamType, float> mutationParams{
-			// all alleles initialised at a single value
-			pair<GenParamType, float>{GenParamType::SHAPE, gammaMutShapeParam},
-			pair<GenParamType, float>{GenParamType::SCALE, gammaMutScaleParam}
-		};
-		const map<GenParamType, float> placeholderParams = mutationParams;
+			// Create species trait
+			const map<GenParamType, float> mutationParams{
+				// all alleles initialised at a single value
+				pair<GenParamType, float>{GenParamType::SHAPE, gammaMutShapeParam},
+				pair<GenParamType, float>{GenParamType::SCALE, gammaMutScaleParam}
+			};
+			const map<GenParamType, float> placeholderParams = mutationParams;
+
+			SpeciesTrait* spTr = new SpeciesTrait(
+				TraitType::GENETIC_LOAD1,
+				sex_t::NA,
+				createTestGenePositions(genomeSz),
+				ExpressionType::MULTIPLICATIVE,
+				DistributionType::NONE, placeholderParams, // not used for genetic load
+				DistributionType::GAMMA, placeholderParams, // doesn't matter for this test
+				true,
+				1.0, // every site mutates
+				DistributionType::GAMMA, mutationParams,
+				isDiploid ? 2 : 1
+			);
+
+			// Create individual trait object
+			GeneticFitnessTrait traitInd(spTr); // initialisation constructor
+			traitInd.mutate();
+			for (int i = 0; i < genomeSz; i++) {
+				float valAllele = traitInd.getAlleleValueAtLocus(0, i);
+				assert(valAllele <= 1.0);
+			}
+		}
 
-		SpeciesTrait* spTr = new SpeciesTrait(
-			TraitType::GENETIC_LOAD1,
-			sex_t::NA,
-			createTestGenePositions(genomeSz),
-			ExpressionType::MULTIPLICATIVE,
-			DistributionType::NONE, placeholderParams, // not used for genetic load
-			DistributionType::GAMMA, placeholderParams, // doesn't matter for this test
-			true,
-			1.0, // every site mutates
-			DistributionType::GAMMA, mutationParams,
-			isDiploid ? 2 : 1
-		);
+		{
+			// 1/2 chance to sample a mutation < -1
+			const float normalMutMeanParam = 0;
+			const float normalMutSdParam = 1.0;
 
-		// Create individual trait object
-		GeneticFitnessTrait traitInd(spTr); // initialisation constructor
-		traitInd.mutate();
-		for (int i = 0; i < genomeSz; i++) {
-			float valAllele = traitInd.getAlleleValueAtLocus(0, i);
-			assert(valAllele <= 1.0);
+			const int genomeSz = 10;
+			const bool isDiploid{ false };
+
+			// Create species trait
+			const map<GenParamType, float> mutationParams{
+				// all alleles initialised at a single value
+				pair<GenParamType, float>{GenParamType::MEAN, normalMutMeanParam},
+				pair<GenParamType, float>{GenParamType::SD, normalMutSdParam}
+			};
+			const map<GenParamType, float> placeholderParams = mutationParams;
+
+			SpeciesTrait* spTr = new SpeciesTrait(
+				TraitType::GENETIC_LOAD1,
+				sex_t::NA,
+				createTestGenePositions(genomeSz),
+				ExpressionType::MULTIPLICATIVE,
+				DistributionType::NONE, placeholderParams, // not used for genetic load
+				DistributionType::NORMAL, placeholderParams, // doesn't matter for this test
+				true,
+				1.0, // every site mutates
+				DistributionType::NORMAL, mutationParams,
+				isDiploid ? 2 : 1
+			);
+
+			// Create individual trait object
+			GeneticFitnessTrait traitInd(spTr); // initialisation constructor
+			traitInd.mutate();
+			for (int i = 0; i < genomeSz; i++) {
+				float valAllele = traitInd.getAlleleValueAtLocus(0, i);
+				assert(valAllele > -1.0);
+			}
 		}
 	}
+
 }
 
 bool haveSameEmigD0Allele(const Individual& indA, const Individual& indB, const int& position, short whichHaplo = 0) {