diff --git a/src/pke/lib/scheme/ckksrns/ckksrns-parametergeneration.cpp b/src/pke/lib/scheme/ckksrns/ckksrns-parametergeneration.cpp
index 7933fe01..4c86c732 100644
--- a/src/pke/lib/scheme/ckksrns/ckksrns-parametergeneration.cpp
+++ b/src/pke/lib/scheme/ckksrns/ckksrns-parametergeneration.cpp
@@ -219,22 +219,31 @@ bool ParameterGenerationCKKSRNS::ParamsGenCKKSRNS(std::shared_ptr<CryptoParamete
         const auto pos = std::find(moduliQ.begin() + 1, moduliQ.end(), moduliQ[0]);
         if (pos != moduliQ.end()) {
             moduliQ[0] = NextPrime<NativeInteger>(maxPrime, cyclOrder);
-            maxPrime   = moduliQ[0];
         }
     }
+    if (moduliQ[0] > maxPrime)
+        maxPrime = moduliQ[0];
+
     rootsQ[0] = RootOfUnity(cyclOrder, moduliQ[0]);
 
     if (scalTech == FLEXIBLEAUTOEXT) {
-        // find if the value of moduliQ[0] is already in the vector starting with moduliQ[1] and
-        // if there is, then get another prime for moduliQ[0]
-        const auto pos = std::find(moduliQ.begin(), moduliQ.end(), moduliQ[numPrimes]);
-        if (pos == moduliQ.end()) {
+        // find if the value of moduliQ[numPrimes] is already in the vector.
+        // in this case we must redefine the position of "end()" as "end()-1"
+        // currently "moduliQ[numPrimes] == 0" as it is not set up anywhere in this code yet
+        const auto endPos = moduliQ.end() - 1;
+        auto pos          = std::find(moduliQ.begin(), endPos, moduliQ[numPrimes]);
+        if (pos == endPos) {
             // no need for extra checking as extraModSize is automatically chosen by the library
             moduliQ[numPrimes] = FirstPrime<NativeInteger>(extraModSize - 1, cyclOrder);
         }
         else {
             moduliQ[numPrimes] = NextPrime<NativeInteger>(maxPrime, cyclOrder);
-            // maxPrime   = moduliQ[numPrimes];
+            maxPrime           = moduliQ[numPrimes];
+        }
+
+        pos = std::find(moduliQ.begin(), endPos, moduliQ[numPrimes]);
+        if (pos != endPos) {
+            moduliQ[numPrimes] = NextPrime<NativeInteger>(maxPrime, cyclOrder);
         }
 
         rootsQ[numPrimes] = RootOfUnity(cyclOrder, moduliQ[numPrimes]);
diff --git a/src/pke/unittest/utckksrns/UnitTestCKKSrns.cpp b/src/pke/unittest/utckksrns/UnitTestCKKSrns.cpp
index 156f3af0..a8c7fa94 100644
--- a/src/pke/unittest/utckksrns/UnitTestCKKSrns.cpp
+++ b/src/pke/unittest/utckksrns/UnitTestCKKSrns.cpp
@@ -64,6 +64,7 @@ enum TEST_CASE_TYPE {
     ADD_PACKED_PRECISION,
     MULT_PACKED_PRECISION,
     EVALSQUARE,
+    SMALL_SCALING_MOD_SIZE,
 };
 
 static std::ostream& operator<<(std::ostream& os, const TEST_CASE_TYPE& type) {
@@ -114,6 +115,9 @@ static std::ostream& operator<<(std::ostream& os, const TEST_CASE_TYPE& type) {
         case EVALSQUARE:
             typeName = "EVALSQUARE";
             break;
+        case SMALL_SCALING_MOD_SIZE:
+            typeName = "SMALL_SCALING_MOD_SIZE";
+            break;
         default:
             typeName = "UNKNOWN";
             break;
@@ -517,6 +521,10 @@ static std::vector<TEST_CASE_UTCKKSRNS> testCases = {
     { EVALSQUARE, "07", {CKKSRNS_SCHEME, RING_DIM, 7,     DFLT,     DSIZE, BATCH,   DFLT,       DFLT,          DFLT,     HEStd_NotSet, BV,     FLEXIBLEAUTOEXT, DFLT,    DFLT,  DFLT,   DFLT,      DFLT, DFLT,     DFLT,    DFLT}, },
     { EVALSQUARE, "08", {CKKSRNS_SCHEME, RING_DIM, 7,     DFLT,     DSIZE, BATCH,   DFLT,       DFLT,          DFLT,     HEStd_NotSet, HYBRID, FLEXIBLEAUTOEXT, DFLT,    DFLT,  DFLT,   DFLT,      DFLT, DFLT,     DFLT,    DFLT}, },
 #endif
+    // ==========================================
+    // TestType,              Descr, Scheme,        RDim,   MultDepth, SModSize, DSize, BatchSz, SecKeyDist, MaxRelinSkDeg, FModSize, SecLvl,       KSTech, ScalTech,    LDigits, PtMod, StdDev, EvalAddCt, KSCt, MultTech, EncTech, PREMode
+    { SMALL_SCALING_MOD_SIZE, "01", {CKKSRNS_SCHEME, 32768, 19,        22,       DFLT,  DFLT,    DFLT,       DFLT,          23,       DFLT,         DFLT,   FIXEDMANUAL, DFLT,    DFLT,  DFLT,   DFLT,      DFLT, DFLT,     DFLT,    DFLT}, },
+    { SMALL_SCALING_MOD_SIZE, "02", {CKKSRNS_SCHEME, 32768, 16,        50,       DFLT,  DFLT,    DFLT,       DFLT,          50,       HEStd_NotSet, DFLT,   DFLT,        DFLT,    DFLT,  DFLT,   DFLT,      DFLT, DFLT,     DFLT,    DFLT}, },
 #endif
     // ==========================================
 };
@@ -2143,6 +2151,28 @@ class UTCKKSRNS : public ::testing::TestWithParam<TEST_CASE_UTCKKSRNS> {
             std::string name("EMSCRIPTEN_UNKNOWN");
 #else
             std::string name(demangle(__cxxabiv1::__cxa_current_exception_type()->name()));
+#endif
+            std::cerr << "Unknown exception of type \"" << name << "\" thrown from " << __func__ << "()" << std::endl;
+            // make it fail
+            EXPECT_TRUE(0 == 1) << failmsg;
+        }
+    }
+
+    void UnitTest_Small_ScalingModSize(const TEST_CASE_UTCKKSRNS& testData,
+                                       const std::string& failmsg = std::string()) {
+        try {
+            CryptoContext<Element> cc(UnitTestGenerateContext(testData.params));
+        }
+        catch (std::exception& e) {
+            std::cerr << "Exception thrown from " << __func__ << "(): " << e.what() << std::endl;
+            // make it fail
+            EXPECT_TRUE(0 == 1) << failmsg;
+        }
+        catch (...) {
+#if defined EMSCRIPTEN
+            std::string name("EMSCRIPTEN_UNKNOWN");
+#else
+            std::string name(demangle(__cxxabiv1::__cxa_current_exception_type()->name()));
 #endif
             std::cerr << "Unknown exception of type \"" << name << "\" thrown from " << __func__ << "()" << std::endl;
             // make it fail
@@ -2226,6 +2256,10 @@ TEST_P(UTCKKSRNS, CKKSRNS) {
             break;
         case EVALSQUARE:
             UnitTest_EvalSquare(test, test.buildTestName());
+            break;
+        case SMALL_SCALING_MOD_SIZE:
+            UnitTest_Small_ScalingModSize(test, test.buildTestName());
+            break;
         default:
             break;
     }