diff --git a/src/LanguageServer.jl b/src/LanguageServer.jl
index d784cfdb..f9a35a30 100644
--- a/src/LanguageServer.jl
+++ b/src/LanguageServer.jl
@@ -17,6 +17,71 @@ using .URIs2
 
 JSON.lower(uri::URI) = string(uri)
 
+# these are the endpoints of JSON-RPC error codes
+# per the LSP spec, no LSP error codes should lie
+# between these
+const SERVER_ERROR_END       = -32000
+const SERVER_ERROR_START     = -32099
+
+# These are existing reserved errors for JSONRPC.jl
+# We shouldn't throw these manually
+const SERVER_NOT_INITIALIZED = -32002
+const UNKNOWN_ERROR_CODE     = -32001
+
+# LSP specific error codes
+# these are the defined ranges for LSP errors
+# not real error codes. Custom errors must lie
+# outside this range
+const LSP_RESERVED_ERROR_START = -32899
+const LSP_RESERVED_ERROR_END   = -32800
+
+const REQUEST_CANCELLED      = -32800
+const CONTENT_MODIFIED       = -32801
+const SERVER_CANCELLED       = -32802
+const REQUEST_FAILED         = -32803
+
+# Specific to our implementation
+const FORMATTING_FAILED  = -33000
+const NO_DOCUMENT        = -33100
+const MISMATCHED_VERSION = -33101
+const SHUTDOWN_REQUEST   = -32600
+
+const ERROR_CODES = (
+    REQUEST_CANCELLED,
+    CONTENT_MODIFIED,
+    SERVER_CANCELLED,
+    REQUEST_FAILED,
+    FORMATTING_FAILED,
+    NO_DOCUMENT,
+    MISMATCHED_VERSION,
+    SHUTDOWN_REQUEST
+)
+
+function __init__()
+    # init JSONRPC error messages
+    conflicting_codes = filter(ERROR_CODES) do code
+        !haskey(JSONRPC.JSONRPCErrorStrings, code) && return false
+        return JSONRPC.JSONRPCErrorStrings[code] != "ServerError"
+    end
+    # if any of the codes we want to use are already set,
+    # it means we have a conflict with another application
+    # using JSONRPC.jl at the same time in this process
+    # warn the user of this, so that they can debug/work around it
+    if !isempty(conflicting_codes)
+        @warn """JSONRPC Error Codes conflict!
+
+        Another library besides LanguageServer.jl is using JSONRPC.jl with conflicting error codes.
+        LanguageServer.jl will overwrite this with its own state. Faulty behavior/error printing may arise.
+        """ Codes=conflicting_codes
+    end
+
+    JSONRPC.RPCErrorStrings[REQUEST_CANCELLED]      = "RequestCancelled"
+    JSONRPC.RPCErrorStrings[CONTENT_MODIFIED]       = "ContentModified"
+    JSONRPC.RPCErrorStrings[SERVER_CANCELLED]       = "ServerCancelled"
+    JSONRPC.RPCErrorStrings[REQUEST_FAILED]         = "RequestFailed"
+    nothing
+end
+
 include("exception_types.jl")
 include("protocol/protocol.jl")
 include("extensions/extensions.jl")
diff --git a/src/languageserverinstance.jl b/src/languageserverinstance.jl
index e207fb59..f90b41b4 100644
--- a/src/languageserverinstance.jl
+++ b/src/languageserverinstance.jl
@@ -257,7 +257,7 @@ function request_wrapper(func, server::LanguageServerInstance)
             # it's fine to always return a value here, even for notifications, because
             # JSONRPC discards it anyways in that case
             return JSONRPC.JSONRPCError(
-                -32600,
+                SHUTDOWN_REQUEST,
                 "LS shutdown was requested.",
                 nothing
             )
diff --git a/src/requests/features.jl b/src/requests/features.jl
index 9d232b64..0652ec57 100644
--- a/src/requests/features.jl
+++ b/src/requests/features.jl
@@ -160,7 +160,7 @@ function textDocument_formatting_request(params::DocumentFormattingParams, serve
         format_text(get_text(doc), params, config)
     catch err
         return JSONRPC.JSONRPCError(
-            -32000,
+            FORMATTING_FAILED,
             "Failed to format document: $err.",
             nothing
         )
@@ -210,7 +210,7 @@ function textDocument_range_formatting_request(params::DocumentRangeFormattingPa
         format_text(text_marked, params, config)
     catch err
         return JSONRPC.JSONRPCError(
-            -33000,
+            FORMATTING_FAILED,
             "Failed to format document: $err.",
             nothing
         )
diff --git a/src/utilities.jl b/src/utilities.jl
index 73487f04..f91b187d 100644
--- a/src/utilities.jl
+++ b/src/utilities.jl
@@ -3,7 +3,7 @@
 
 function nodocument_error(uri, data=nothing)
     return JSONRPC.JSONRPCError(
-        -33100,
+        NO_DOCUMENT,
         "document $(uri) requested but not present in the JLS",
         data
     )
@@ -11,7 +11,7 @@ end
 
 function mismatched_version_error(uri, doc, params, msg, data=nothing)
     return JSONRPC.JSONRPCError(
-        -33101,
+        MISMATCHED_VERSION,
         "version mismatch in $(msg) request for $(uri): JLS $(get_version(doc)), client: $(params.version)",
         data
     )