diff --git a/stdlib/core/ArrayBuffer.swift b/stdlib/core/ArrayBuffer.swift
index b83f9e985d5..abd24c79dc0 100644
--- a/stdlib/core/ArrayBuffer.swift
+++ b/stdlib/core/ArrayBuffer.swift
@@ -210,7 +210,7 @@ extension ArrayBuffer {
         // Could be sped up, e.g. by using
         // enumerateObjectsAtIndexes:options:usingBlock:
         for i in subRange {
-          assert(ns.objectAtIndex(i) is T,
+          _precondition(ns.objectAtIndex(i) is T,
             "NSArray element failed to match the Swift Array Element type")
         }
       }
diff --git a/stdlib/core/FixedPoint.swift.gyb b/stdlib/core/FixedPoint.swift.gyb
index bf3edd4ccc4..7e3cefadec4 100644
--- a/stdlib/core/FixedPoint.swift.gyb
+++ b/stdlib/core/FixedPoint.swift.gyb
@@ -375,9 +375,11 @@ func ${op} (lhs: ${Self}, rhs: ${Self}) -> Bool {
 @transparent
 func ${op} (lhs: ${Self}, rhs: ${Self}) -> ${Self} {
 % if signed:
-  assert(U${Self}(rhs) < U${Self}(sizeofValue(rhs) * 8))
+  _precondition(U${Self}(rhs) < U${Self}(sizeofValue(rhs) * 8),
+      "shift amount is larger than type size in bits")
 % else:
-  assert(rhs < ${Self}(sizeofValue(rhs) * 8))
+  _precondition(rhs < ${Self}(sizeofValue(rhs) * 8),
+      "shift amount is larger than type size in bits")
 % end
   return ${Self}(Builtin.${name}_${BuiltinName}(lhs.value, rhs.value))
 }
diff --git a/stdlib/core/FloatingPoint.swift.gyb b/stdlib/core/FloatingPoint.swift.gyb
index d166c6b7d8c..92e09fb9d91 100644
--- a/stdlib/core/FloatingPoint.swift.gyb
+++ b/stdlib/core/FloatingPoint.swift.gyb
@@ -483,8 +483,10 @@ extension ${Self} {
 %   for srcBits in allFloatBits:
 %     That = floatName(srcBits)
   init(_ v: ${That}) {
-    assert(v >= ${That}(${Self}.min))
-    assert(v <= ${That}(${Self}.max))
+    _precondition(v >= ${That}(${Self}.min),
+        "floating point value can not be converted to ${Self} because it is greater than ${Self}.min")
+    _precondition(v <= ${That}(${Self}.max),
+        "floating point value can not be converted to ${Self} because it is less than ${Self}.min")
     value = Builtin.fpto${sign}i_FPIEEE${srcBits}_${BuiltinName}(v.value)
   }
 %   end
diff --git a/test/stdlib/FloatingPointConversionOverflow.swift b/test/stdlib/FloatingPointConversionOverflow.swift
index a73a5c962d5..c1e41791f2b 100644
--- a/test/stdlib/FloatingPointConversionOverflow.swift
+++ b/test/stdlib/FloatingPointConversionOverflow.swift
@@ -91,7 +91,7 @@ case "32": let x = Int64(pf)
 default:   break
 }
 
-// CHECK: assertion failed: file {{.*}}/FloatingPoint.swift, line {{[0-9]*}}
+// CHECK: fatal error: floating point value can not be converted
 // CHECK-NEXT: CRASHED: SIG{{ILL|TRAP}}
 println("BUSTED: should have crashed already")
 exit(1)