diff --git a/common/tcp_connection.h b/common/tcp_connection.h
index ae02b9c56..c3fa5cd51 100644
--- a/common/tcp_connection.h
+++ b/common/tcp_connection.h
@@ -23,7 +23,9 @@
 */
 
 #ifdef _WINDOWS
-	#define snprintf	_snprintf
+	#if (!defined(_MSC_VER) || (defined(_MSC_VER) && _MSC_VER < 1900))
+		#define snprintf	_snprintf
+	#endif
 	#define strncasecmp	_strnicmp
 	#define strcasecmp	_stricmp
 
diff --git a/common/types.h b/common/types.h
index 2e1b5d3f3..b3be97d32 100644
--- a/common/types.h
+++ b/common/types.h
@@ -43,7 +43,9 @@ typedef unsigned char		uchar;
 typedef const char Const_char;	//for perl XS
 
 #ifdef _WINDOWS
-	#define snprintf	_snprintf
+	#if (!defined(_MSC_VER) || (defined(_MSC_VER) && _MSC_VER < 1900))
+		#define snprintf	_snprintf
+	#endif
 	#define strncasecmp	_strnicmp
 	#define strcasecmp	_stricmp
 	typedef void ThreadReturnType;
diff --git a/zone/beacon.cpp b/zone/beacon.cpp
index 0df02b201..21943ecee 100644
--- a/zone/beacon.cpp
+++ b/zone/beacon.cpp
@@ -26,8 +26,10 @@ target to center around.
 class Zone;
 
 #ifdef _WINDOWS
-    #define snprintf	_snprintf
-    #define vsnprintf	_vsnprintf
+	#if (!defined(_MSC_VER) || (defined(_MSC_VER) && _MSC_VER < 1900))
+		#define snprintf	_snprintf
+		#define vsnprintf	_vsnprintf
+	#endif
     #define strncasecmp	_strnicmp
     #define strcasecmp	_stricmp
 #endif
diff --git a/zone/bonuses.cpp b/zone/bonuses.cpp
index 155dfc4ae..3821592cb 100644
--- a/zone/bonuses.cpp
+++ b/zone/bonuses.cpp
@@ -38,7 +38,6 @@
 #include "../common/unix.h"
 #endif
 
-
 void Mob::CalcBonuses()
 {
 	CalcSpellBonuses(&spellbonuses);
@@ -3493,6 +3492,17 @@ uint8 Mob::IsFocusEffect(uint16 spell_id,int effect_index, bool AA,uint32 aa_eff
 	return 0;
 }
 
+// Avoid an internal compiler error in VS 2015 
+// Community RC (free) with the /O2 compiler
+// option enabled on x64 build; definite fail on
+// building Release-X64.  Disabling optimizations
+// for the entire file might be overkill and/or
+// inapplicable to other builds, more testing needed.
+// Bug has been reported to MS, fix ETA unknown.
+#if (defined(_MSC_VER) && defined(_WIN64)&& _MSC_VER==1900)
+#pragma optimize( "", off )
+#endif
+
 void Mob::NegateSpellsBonuses(uint16 spell_id)
 {
 	if(!IsValidSpell(spell_id))
@@ -4654,6 +4664,7 @@ void Mob::NegateSpellsBonuses(uint16 spell_id)
 						itembonuses.SkillProcSuccess[e] = effect_value;
 						aabonuses.SkillProcSuccess[e] = effect_value;
 					}
+					break;
 				 }
 
 				case SE_SkillProc:{
@@ -4663,9 +4674,14 @@ void Mob::NegateSpellsBonuses(uint16 spell_id)
 						itembonuses.SkillProc[e] = effect_value;
 						aabonuses.SkillProc[e] = effect_value;
 					}
+					break;
 				 }
 			}
 		}
 	}
 }
 
+// See line 3495 above, more or less
+#if (defined(_MSC_VER) && defined(_WIN64)&& _MSC_VER==1900)
+	#pragma optimize( "", on )
+#endif
diff --git a/zone/corpse.cpp b/zone/corpse.cpp
index af937e41b..b0e9bef0d 100644
--- a/zone/corpse.cpp
+++ b/zone/corpse.cpp
@@ -22,8 +22,10 @@ Child of the Mob class.
 */
 
 #ifdef _WINDOWS
-    #define snprintf	_snprintf
-	#define vsnprintf	_vsnprintf
+	#if (!defined(_MSC_VER) || (defined(_MSC_VER) && _MSC_VER < 1900))
+		#define snprintf	_snprintf
+		#define vsnprintf	_vsnprintf
+	#endif
     #define strncasecmp	_strnicmp
     #define strcasecmp	_stricmp
 #endif
diff --git a/zone/encounter.cpp b/zone/encounter.cpp
index 1f77de43a..01d4ef670 100644
--- a/zone/encounter.cpp
+++ b/zone/encounter.cpp
@@ -17,10 +17,12 @@ Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
 
 #ifdef _WINDOWS
-#define snprintf	_snprintf
-#define vsnprintf	_vsnprintf
-#define strncasecmp	_strnicmp
-#define strcasecmp	_stricmp
+	#if (!defined(_MSC_VER) || (defined(_MSC_VER) && _MSC_VER < 1900))
+		#define snprintf	_snprintf
+		#define vsnprintf	_vsnprintf
+	#endif
+	#define strncasecmp	_strnicmp
+	#define strcasecmp	_stricmp
 #endif
 
 #include "../common/races.h"