diff --git a/cmake/Platform.cmake b/cmake/Platform.cmake
index 86f70ada10e..13774663e2e 100644
--- a/cmake/Platform.cmake
+++ b/cmake/Platform.cmake
@@ -32,7 +32,13 @@ if (MSVC)
     # /w34127
     # Enable warning under W3: conditional expression is constant
 
-    add_compile_options(/wd4267 /wd4819 /wd26812 /w34127)
+    # /w34702
+    # Enable warning under W3: unreachable code
+
+    # /w35262
+    # Enable warning under W3: implicit fall-through occurs here; are you missing a break statement?
+
+    add_compile_options(/wd4267 /wd4819 /wd26812 /w34127 /w34702 /w35262)
 
     # Silence all C++17 deprecation warnings, same as in the vcxproj files
     add_compile_definitions(_SILENCE_ALL_CXX17_DEPRECATION_WARNINGS)
diff --git a/ql/math/integrals/exponentialintegrals.cpp b/ql/math/integrals/exponentialintegrals.cpp
index 18ce21ff387..99c6d9ad0af 100644
--- a/ql/math/integrals/exponentialintegrals.cpp
+++ b/ql/math/integrals/exponentialintegrals.cpp
@@ -170,8 +170,6 @@ namespace QuantLib {
                 }
                 return (acc + std::complex<Real>(0.0, sign(z.imag())*M_PI))
                         - std::exp(z)/ (1.0 - z + ei);
-
-                QL_FAIL("series conversion issue for Ei(" << z << ")");
             }
 
             std::complex<Real> s(0.0), sn=z;
diff --git a/ql/pricingengines/vanilla/analytichestonengine.cpp b/ql/pricingengines/vanilla/analytichestonengine.cpp
index f375a6f07a1..1dd91a653f7 100644
--- a/ql/pricingengines/vanilla/analytichestonengine.cpp
+++ b/ql/pricingengines/vanilla/analytichestonengine.cpp
@@ -175,7 +175,7 @@ namespace QuantLib {
         sigma2_(sigma_*sigma_),
         rsigma_(rho*sigma_),
         t0_(kappa - ((j== 1)? rho*sigma : Real(0))),
-        
+
         engine_(engine)
     {
     }
@@ -488,9 +488,11 @@ namespace QuantLib {
                         *(v0 + kappa*theta*term)
                   - 2*kappa*theta*std::atan(rho/std::sqrt(1-rho*rho))))
                           /(sigma*sigma);
+            [[fallthrough]];
           case AngledContour:
             vAvg_ = (1-std::exp(-kappa*term))*(v0 - theta)
                       /(kappa*term) + theta;
+            [[fallthrough]];
           case AngledContourNoCV:
             {
               const Real r = rho - sigma*freq_ / (v0 + kappa*theta*term);
diff --git a/ql/time/ecb.cpp b/ql/time/ecb.cpp
index 71bea514671..0009ee94a91 100644
--- a/ql/time/ecb.cpp
+++ b/ql/time/ecb.cpp
@@ -303,7 +303,6 @@ namespace QuantLib {
             if (incrementAndCheckForOverlow(nextCodeStr[4]))
                 incrementAndCheckForOverlow(nextCodeStr[3]);
         }
-        return nextCodeStr;
 
         #if defined(QL_EXTRA_SAFETY_CHECKS)
         QL_ENSURE(isECBcode(nextCodeStr),